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Objectives We assess how age, the presence of mature adults aged 45+ years, and recent deaths in rural households are associated with coronavirus disease 2019 (COVID-19) preventative actions and the likelihood of getting vaccinated against the virus in Malawi during early stages of the pandemic. Methods We draw upon data from 2,187 rural Malawians who participated in a 2020 COVID-19 Phone Survey. We estimate the log odds of engaging in "low-cost" and "high-cost" COVID-19 preventative actions based on age, gender, household composition, and recent household deaths. Low-cost prevention efforts were washing hands with soap and water frequently, avoiding close contact with people when going out, and avoiding shaking hands. High-cost actions included staying at home and decreasing time spent close to people not living in their household. We also estimate the chances of acquiring the COVID-19 vaccine in early stages of its availability. Results Mature women (45+ years) in general and younger men (<45 years)—living with at least one mature adult in the household—were less likely than others to comply with low-cost actions. Mature men were more likely than younger men (<45 years) to take on high-cost actions. To some extent, individuals who experienced a recent family death were more likely to engage in high-cost COVID-19 preventative actions as well as getting vaccinated. Discussion Gendered age differences in preventing the transmission of COVID-19 offer hints of larger social norms affecting protective efforts. The analyses also inform future COVID-19 public health outreach efforts in Malawi and other rural SSA contexts. [ABSTRACT FROM AUTHOR]

Research on the timing of events during the transition to adulthood, such as first union, sex, and birth in low- and middle-income countries (LMICs), focused predominantly on measures of central tendency, notably median or mean ages. In this report, we adopt a different perspective on this topic by examining disparities in the timing of these events in 46 LMICs spanning four decades. Using Demographic and Health Surveys, we estimate ages at which 25 percent, 50 percent, and 75 percent of women have first union, birth, and sex. We compute interquartile ranges to measure within-country variation and disparities in the timing of sexual initiation and family formation. Variation in the timing of first union, birth, and sex generally increases as the median ages at these events increase. Disparities in the timing of first union and birth grew in West Africa and Latin America, and women who experience these events relatively early increasingly lag behind women who experience them relatively late. Documenting trends in measures of central tendency is insufficient to capture the complexity of ongoing changes because they mask growing disparities in the timing of family formation across many LMICs. These results are important for assessing progress toward the achievement of sustainable development goals related to the reduction of early marriages and pregnancies and highlight a need for more holistic approaches to measure the timing of family formation. [ABSTRACT FROM AUTHOR]

Gender differences in union formation and sexual initiation in sub‐Saharan Africa remain poorly documented, in large part due to a scarcity of research on the transition to adulthood among men. We adopt a novel perspective on this topic by examining gender gaps in the ages at first union and sex in 24 countries, focusing on measures of central tendency and dispersion. Gender differences in age at first union decreased, driven by postponement among women with relatively late union formation. Yet, due to concurrent persistence of early unions among a sizable portion of women's populations, within‐country heterogeneity in ages at first union increased substantially among women. Thus, although forces responsible for earlier union formation among women than men are weakening, these changes affect population strata unequally. Gender differences in age at first sex decreased to a lesser extent, but in some countries, they disappeared or reversed, uncovering a shift in the relationship between gender and timing of sexual initiation. Changes in union formation and sexual initiation are more heterogeneous across countries among men than women, indicating that these processes among men are more context specific. We show importance of studying men's behavior and exploring heterogeneity in union formation and sexual initiation both within and between populations of women and men. [ABSTRACT FROM AUTHOR]

Background: Intimate partner violence (IPV) is prevalent in high- as well as low-income contexts. It results in a substantial public health burden and significant negative socioeconomic and health outcomes throughout the life-course. However, limited knowledge exists about IPV during early adolescence. This period is critical during the transition to adulthood for at least two reasons: it is when the majority of adolescents in low-income countries first encounter dating, sexuality and partnerships, often with older adolescents or adults, and it is also the period when lifelong patterns of violence and norms about acceptable IPV are formed. The current study is one of the first to measure IPV prevalence among young adolescents in a low-income setting, examine the potential etiology, and investigate relationships with gender ideology, poverty, mental health and childhood adversity. Methods: We surveyed 2,089 adolescents aged 10–16 in Malawi using standardized instruments. We estimated the prevalence of IPV, and use multivariate logistic regression to test potential correlates. Results: More than a quarter (27%) of ever-partnered adolescents in Malawi report being victimized. A substantial proportion of both male and female adolescents (15%) report committing violence against their partner. Girls were more likely than boys to report being a victim of sexual IPV (24% versus 8%), and boys more likely to perpetrate such (9% versus 1%). Almost 10% of the sample had both committed and been a victim of IPV. Cumulative childhood adversity (e.g., physical abuse, witnessing domestic violence) was a consistent and strong correlate of IPV victimization (adjusted odds ratio (aOR) 1.30) and of perpetration (aOR 1.35). Depression and PTSD were likewise associated with IPV victimization in the overall sample. Notably, gender ideology was not predictive of either victimization or perpetration, even among boys. Conclusions: IPV is common for both male and female young Malawian adolescents, and includes both victimization and perpetration. IPV compounds other adversities experienced by adolescents in this low-income setting, and it is rarely alleviated through help from the health system or other formal support. These findings underscore the need to intervene early when interventions can still break destructive pathways and help foster healthier relationships. This focus on early adolescence is particularly critical in low-income countries given the early onset and rapid pace of the transition to adulthood, with sexual activity, dating and partnership thus being common already in young adolescence. Promising interventions would be those that reduce violence against or around children, as well as those that reduce the impacts of such trauma on mental health during adolescence. [ABSTRACT FROM AUTHOR]

An increasing number of developing countries are experiencing below replacement fertility rates. Although the factors associated with low fertility in developed countries have been widely explored in the literature, studies of low fertility in middle- and low-income countries continue to be rare. To help fill this gap, Brazil was used as a case study to assess whether human development, gender equality and the ability of mothers with young children to work are associated with the likelihood of married or cohabiting women to have a child. For this purpose, multilevel logistic regressions were estimated using the 1991, 2000 and 2010 Brazilian Demographic Censuses. It was found that human development was negatively associated with fertility in the three periods analysed. Gender equality and the ability of mothers with young children to work were positively associated with the odds of having higher order births in Brazil in 2000 and 2010. In 1991, these variables were not associated with higher order births, and gender equality was negatively associated with first births. The positive association found in 2000 and 2010 may constitute a reversal of the relationship that in all likelihood prevailed earlier in the demographic transition when gender equality was most likely negatively correlated with fertility levels. [ABSTRACT FROM AUTHOR]

Biodegradable polyesters have the potential to replace nondegradable, persistent polymers in numerous applications and thereby alleviate plastic accumulation in the environment. Herein, we present an analytical approach to study enzymatic hydrolysis of polyesters, the key step in their overall biodegradation process. The approach is based on embedding fluorescein dilaurate (FDL), a fluorogenic ester substrate, into the polyester matrix and on monitoring the enzymatic cohydrolysis of FDL to fluorescein during enzymatic hydrolysis of the polyester. We validated the approach against established techniques using FDL-containing poly(butylene adipate) films and Fusarium solani cutinase (FsC). Implemented on a microplate reader platform, the FDL-based approach enabled sensitive and high-throughput analysis of the enzymatic hydrolysis of eight aliphatic polyesters by two fungal esterases (FsC and Rhizopus oryzae lipase) at different temperatures. While hydrolysis rates for both enzymes increased with decreasing differences between the polyester melting temperatures and the experimental temperatures, this trend was more pronounced for the lipase than the cutinase. These trends in rates could be ascribed to a combination of temperature-dependent polyester chain flexibility and accessibility of the enzyme active site. The work highlights the capability of the FDL-based approach to be utilized in both screening and mechanistic studies of enzymatic polyester hydrolysis. [ABSTRACT FROM AUTHOR]

Compound-specific isotope analysis (CSIA) is a promising approach for tracking biotransformation of organic pollutants, but isotope fractionation associated with aromatic oxygenations is only poorly understood. We investigated the dioxygenation of a series of nitroaromatic compounds to the corresponding catechols by two enzymes, namely, nitrobenzene and 2-nitrotoluene dioxygenase (NBDO and 2NTDO) to elucidate the enzyme- and substrate-specificity of C and H isotope fractionation. While the apparent 13C- and 2H-kinetic isotope effects of nitrobenzene, nitrotoluene isomers, 2,6-dinitrotoluene, and naphthalene dioxygenation by NBDO varied considerably, the correlation of C and H isotope fractionation revealed a common mechanism for nitrobenzene and nitrotoluenes. Similar observations were made for the dioxygenation of these substrates by 2NTDO. Evaluation of reaction kinetics, isotope effects, and commitment-to-catalysis based on experiment and theory showed that rates of dioxygenation are determined by the enzymatic O2 activation and aromatic C oxygenation. The contribution of enzymatic O2 activation to the reaction rate varies for different nitroaromatic substrates of NBDO and 2NTDO. Because aromatic dioxygenation by nonheme iron dioxygenases is frequently the initial step of biodegradation, O2 activation kinetics may also have been responsible for the minor isotope fractionation reported for the oxygenation of other aromatic contaminants. [ABSTRACT FROM AUTHOR]

Female empowerment and positive attitudes towards women’s rights in sexual relationships have been found to be key elements of successful behaviour-based HIV prevention programmes. However, HIV prevention programmes that do not specifically engage with gender issues may also affect attitudes and beliefs towards women’s rights within sexual relationships. Using data from the Malawi Longitudinal Study of Families and Health we compare measures of female empowerment and changing gender norms between intervention participants and non-participants. Results suggest that female intervention participants were more likely than non-participants to believe that: (1) women have more rights within sexual relationships in general and (2) women have the right to protect themselves against HIV risk (indicating possible increases in female self-efficacy in making HIV prevention decisions). Male intervention participants showed no substantial positive change in attitudes towards women’s rights. These results highlight an important positive effect of HIV prevention programmes on women’s attitudes towards their own rights. [ABSTRACT FROM PUBLISHER]

Cleavage of ester bonds by extracellular microbial hydrolases is considered a key step during the breakdown of biodegradable polyester materials in natural and engineered systems. Here we present a novel analytical approach for simultaneous detection of changes in the masses and rigidities of polyester thin films during enzymatic hydrolysis using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). In experiments with poly(butylene succinate) (PBS) and the lipase of Rhizopus oryzae (RoL), we detected complete hydrolysis of PBS thin films at pH 5 and 40 °C that proceeded through soft and water-rich film intermediates. Increasing the temperature from 20 to 40 °C resulted in a larger increase of the enzymatic hydrolysis rate of PBS than of nonpolymeric dibutyl adipate. This finding was ascribed to elevated accessibility of ester bonds to the catalytic site of RoL due to increasing polyester chain mobility. When the pH of the solution was changed from 5 to 7, initial hydrolysis rates were little affected, while a softer film intermediate that lead to incomplete film hydrolysis was formed. Hydrolysis dynamics of PBS, poly(butylene adipate), poly(lactic acid), and poly(ethylene terephthalate) in assays with RoL showed distinct differences that we attribute to differences in the polyester structure. [ABSTRACT FROM AUTHOR]

While new empirical findings and theoretical frameworks provide insight into the interrelations between socioeconomic development, gender equity, and low fertility, puzzling exceptions and outliers in these findings call for a more all-encompassing framework to understand the interplay between these processes. We argue that the pace and onset of development are two important factors to be considered when analyzing gender equity and fertility. Within the developed world, 'first-wave developers'-or countries that began socioeconomic development in the nineteenth/early twentieth century-currently have much higher fertility levels than 'late developers.' We lay out a novel theoretical approach to explain why this is the case and provide empirical evidence to support our argument. Our approach not only explains historical periods of low fertility but also sheds light on why there exists such large variance in fertility rates among today's developed countries. [ABSTRACT FROM AUTHOR]

The Malawi Longitudinal Study of Families and Health (MLSFH) is one of very few longstanding, publicly available longitudinal cohort studies in a sub-Saharan African (SSA) context. It provides a rare record of more than a decade of demographic, socioeconomic and health conditions in one of the world's poorest countries. The MLSFH was initially established in 1998 to study social network influences on fertility behaviours and HIV risk perceptions, and over time the focus of the study expanded to include health, sexual behaviours, intergenerational relations and family/household dynamics. The currently available data include MLSFH rounds collected in 1998, 2001, 2004, 2006, 2008, 2010 and 2012 for up to 4000 individuals, providing information about socioeconomic and demographic characteristics, sexual behaviours, marriage, household/family structure, risk perceptions, social networks and social capital, intergenerational relations, HIV/AIDS and other dimensions of health. The MLSFH public use data can be requested on the project website: http://www.malawi.pop.upenn.edu/. [ABSTRACT FROM AUTHOR]

This article assesses how married individuals' knowledge of HIV status gained through HIV testing and counseling (HTC) affects divorce, the number of sexual partners, and the use of condoms within marriage. This study improves upon previous studies on this topic because the randomized incentives affecting the propensity to be tested for HIV permit control for selective testing. Instrumental variable probit and linear models are estimated, using a randomized experiment administered as part of the Malawi Longitudinal Study of Families and Health (MLSFH). The results indicate that knowledge of HIV status (1) does not affect chances of divorce for either HIV-negative or HIV-positive respondents; (2) reduces the number of reported sexual partners among HIV-positive respondents; and (3) increases reported condom use with spouses for both HIV-negative and HIV-positive respondents. These results imply that individuals actively respond to information about their HIV status that they learn during HTC, invoking protective behavior against future risk of HIV/AIDS for themselves and their actual and potential sexual partners. Some limitations of this study are a small sample size for those who are HIV-positive and dependence on self-reported sexual behaviors. [ABSTRACT FROM AUTHOR]

Oxygenation of aromatic rings is a frequent initial step in the biodegradation of persistent contaminants, and the accompanying isotope fractionation is increasingly used to assess the extent of transformation in the environment. Here, we systematically investigated the dioxygenation of two nitroaromatic compounds (nitrobenzene and 2-nitrotoluene) by nitrobenzene dioxygenase (NBDO) to obtain insights into the factors governing its C, H, and N isotope fractionation. Experiments were carried out at different levels of biological complexity from whole bacterial cells to pure enzyme. C, H, and N isotope enrichment factors and kinetic isotope effects (KIEs) were derived from the compound-specific isotope analysis of nitroarenes, whereas C isotope fractionation was also quantified in the oxygenated reaction products. Dioxygenation of nitrobenzene to catechol and 2-nitrotoluene to 3-methylcatechol showed large C isotope enrichment factors, ∊C, of -4.1 ± 0.2‰ and -2.5 ± 0.2‰, respectively, and was observed consistently in the substrates and dioxygenation products. ∊H- and ∊N-values were smaller, that is -5.7 ± 1.3‰ and -1.0 ± 0.3‰, respectively. C isotope fractionation was also identical in experiments with whole bacterial cells and pure enzymes. The corresponding 13C-KIEs for the dioxygenation of nitrobenzene and 2-nitrotoluene were 1.025 ± 0.001 and 1.018 ± 0.001 and suggest a moderate substrate specificity. Our study illustrates that dioxygenation of nitroaromatic contaminants exhibits a large C isotope fractionation, which is not masked by substrate transport and uptake processes and larger than dioxygenation of other aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Fertility throughout East Asia has fallen rapidly over the last five decades and is now below the replacement rate of 2.1 in every country in the region. Using South Korea as a case study, we argue that East Asia's ultra-low fertility rates can be partially explained by the steadfast parental drive to have competitive and successful children. Parents throughout the region invest large amounts of time and money to ensure that their children are able to enter prestigious universities and obtain top jobs. Accordingly, childrearing has become so expensive that the average couple cannot afford to have more than just one or two children. The trend of high parental investment in child education, also known as ‘education fever’, exemplifies the notion of ‘quality over quantity’ and is an important contributing factor to understanding low-fertility in East Asia. [ABSTRACT FROM PUBLISHER]

We investigate the causal impact of learning HIV status on HIV/AIDS-related expectations and sexual behavior in the medium run. Our analyses document several unexpected results about the effect of learning one's own, or one's spouse's, HIV status. For example, receiving an HIV-negative test result implies higher subjective expectations about being HIV-positive after two years, and individuals tend to have larger prediction errors about their HIV status after learning their HIV status. If individuals in HIV-negative couples also learn the status of their spouse, these effects disappear. In terms of behavioral outcomes, our analyses document that HIV-positive individuals who learned their status reported having fewer partners and using condoms more often than those who did not learn their status. Among married respondents in HIV-negative couples, learning only one's own status increases risky behavior, while learning both statuses decreases risky behavior. In addition, individuals in sero-discordant couples who learned both statuses are more likely to report some condom use. Overall, our analyses suggest that ensuring that each spouse learns the HIV status of the other, either through couple's testing or through spousal communication, may be beneficial in high-prevalence environments. [ABSTRACT FROM AUTHOR]

Schooling generally is positively associated with better health-related outcomes-for example, less hospitalization and later mortality-but these associations do not measure whether schooling causes better health-related outcomes. Schooling may in part be a proxy for unobserved endowments-including family background and genetics-that both are correlated with schooling and have direct causal effects on these outcomes. This study addresses the schooling-health-gradient issue with twins methodology, using rich data from the Danish Twin Registry linked to population-based registries to minimize random and systematic measurement error biases. We find strong, significantly negative associations between schooling and hospitalization and mortality, but generally no causal effects of schooling. [ABSTRACT FROM AUTHOR]

Twins have been extensively used in economics, sociology, and behavioral genetics to investigate the role of genetic endowments on a broad range of social, demographic, and economic outcomes. However, the focus in these literatures has been distinct: The economic literature has been primarily concerned with the need to control for unobserved endowments-including as an important subset, genetic endowments-in analyses that attempt to establish the impact of one variable, often schooling, on a variety of economic, demographic, and health outcomes. Behavioral genetic analyses have mostly been concerned with decomposing the variation in the outcomes of interest into genetic, shared environmental, and non-shared environmental components, with recent multivariate analyses investigating the contributions of genes and the environment to the correlation and causation between variables. Despite the fact that twins studies and the recognition of the role of endowments are central to both of these literatures, they have mostly evolved independently. In this paper, we develop formally the relationship between the economic and behavioral genetic approaches to the analyses of twins, and we develop an integrative approach that combines the identification of causal effects, which dominates the economic literature, with the decomposition of variances and covariances into genetic and environmental factors that are the primary goal of behavioral genetic approaches. We apply this integrative ACE-β approach to an illustrative investigation of the impact of schooling on several demographic outcomes such as fertility and nuptiality and health. [ABSTRACT FROM AUTHOR]

The article presents a study on the uptake of Human Immunodeficiency Virus (HIV) testing and counseling (HTC) among the poorest families in sub-Saharan countries. Residents and their spouses aging 18 to 35 in six villages in Likoma Island, Malawi, Africa were given home-based HTC services during the study. Results showed that lowest income quartile household members have a little chance to utilize home-based HTC services. The study also suggests the use of HTC to lessen the impact of AIDS.

A wide variety of antibacterial compounds is rapidly oxidized by O3 and hydroxyl radical (*OH) during aqueous ozonation. Quantitative microbiological assays have been developed here or adapted from existing methods and utilized to measure the resulting changes in antibacterial potencies during O3 and *OH treatment of 13 antibacterial molecules (roxfthromycin, azithromycin, tylosin, ciprofloxacin, enrofloxacin, penicillin G, cephalexin, sulfamethoxazole, trimethoprim, lincomycin,tetracycline, vancomycin, and amikacin) from 9 structural classes (macrolides, fluoroquinolones, β-lactams, sulfonamides, dihydrofolate reductase inhibitors, lincosamides, tetracyclines, glycopeptides, and aminoglycosides), as well as the biocide triclosan. Potency measurements were determined from dose-response relationships obtained by exposing Escherichia coli or Bacillus subtiis reference strainsto treated samples of each antibacterial compound via broth micro- or macrodilution assays and related to the measured residual concentrations of parent antibacterial in each sample. Data obtained from these experiments show that O3 and *OH reactions lead in nearly all cases to stoichiometric elimination of antibacterial activity (i.e., loss of 1 mole equivalent of potency per mole of parent compound consumed). The β-lactams penicillin G (PG) and cephalexin (CP) represent the only clear exceptions, as bioassay measurements indicate that biologically active products may be formed in the reactions of these two compounds with both O3 and *OH. The active product(s) generated in the direct reaction of O3 with PG appear(s) to be recalcitrant to further transformation by O3, though any biologically active products formed in the reactions of CP with O3, or of either PG or CP with *OH, are apparently deactivated by further reactions with O3 or *OH, respectively. Thus, with few exceptions, it can be expected that municipal wastewater ozonation will generally yield sufficient structural modification of antibacterial moleculesto eliminate their antibacterial activities,whether oxidation results from selective reactions with O3 or from relatively nonselective reactions with incidentally produced *OH. [ABSTRACT FROM AUTHOR]

This article discusses how European women are historically bearing their first children later than ever before. In the United States and other countries, entry into parenthood is also seeing delays. Many experts argue that such fertility trends in developed countries are characterized by increasing, persistent, and arguably irreversible delays in childbearing in many socioeconomic conditions. Many of the informal age deadlines for childbearing are apparently being challenged and biological limits are being pushed. The article also presents information about the physiological aspects of late fertility and discusses the effect of new technologies on conception and pregnancy. Sweden's late and very late fertility is also examined.

Understanding the determinants of individuals' perceptions of their risk of becoming infected with HIV and their perceptions of acceptable strategies of prevention is an essential step toward curtailing the spread of this disease. We focus in this article on learning and decision-making about AIDS in the context of high uncertainty about the disease and appropriate behavioral responses. We argue that social interactions are important for both. Using longitudinal survey data from rural Kenya and Malawi, we test this hypothesis. We investigate whether social interactions--and especially the extent to which social network partners perceive themselves to be at risk--exert causal influences on respondents' risk perceptions and on one approach to prevention, spousal communication about the threat of AIDS to the couple and their children. The study explicitly allows for the possibility that important characteristics, such as unobserved preferences or community characteristics, determine not only the outcomes of interest but also the size and composition of networks. The most important empirical result is that social networks have significant and substantial effects on risk perceptions and the adoption of new behaviors even after we control for unobserved factors. [ABSTRACT FROM AUTHOR]

This paper reviews several studies that investigated the potential role of genetic factors in determining fertility outcomes. Our review demonstrates convincingly that fertility contains genetic variance; that is, differences between humans in their genetic make-up affects their fertility outcomes and fertility-related behaviours. This finding is robust using both heritabilities and coefficients of genetic variation, and using both direct measures of fertility outcomes and also fertility precursors like fecundity, marriage, fertility expectations and attempts to get pregnant (proception). Moreover, genetic variance can change over short periods of time or across educational levels, specifically for females, and the relevance of genetic variance seems to increase during times of increasing reproductive choice. [ABSTRACT FROM AUTHOR]

The study presented here is an investigation of the importance of social interactions to perceptions of the risk of AIDS, and explores spousal communication about the AIDS epidemic in rural Malawi. A fixed-effects analysis based on longitudinal data collected in 1998 and 2001 shows that social interactions on the subject of HIV/AIDS have significant and substantial effects on respondents’ perceptions of the risk of HIV/AIDS, even after controlling for unobserved factors that affect the selection of social networks. These effects are more complex than previously thought. The dominant mechanisms—social learning and social influence—are found to vary by sex and by region, because of regional variations in the marriage pattern and the resulting implications for the formation of local social networks. The conclusion of the study is that rather than fostering denial and inaction, social interactions are an important vector of change in the face of the HIV/AIDS epidemic. [ABSTRACT FROM AUTHOR]

Economic and rational-choice theories suggest that individuals form unions or have children because these decisions increase their subjective well-being or “happiness.” We investigate this relation using within-MZ (identical) twin pair estimates to control for unobserved factors, such as optimistic preferences, that may simultaneously affect happiness, partnerships, and fertility. Our findings, based on Danish twins aged 25–45 and 50–70 years old, include the following. (1) Currently being in a partnership has large positive effects on happiness. (2) A first child substantially increases well-being, in analyses without controls for partnerships, and males enjoy an almost 75 percent larger happiness gain from a first-born son than from a first-born daughter; however, only females enjoy a happiness gain from the first-born child with controls for partnerships. (3) Additional children beyond the first child have a negative effect on subjective well-being for females, while there is no effect for males. (4) Ever having had children does not significantly affect the subjective well-being of males or females aged 50–70 years. [ABSTRACT FROM AUTHOR]

The article presents the authors' views in response to a comment on their paper "Patterns of Low and Lowest-Low Fertility in Europe," published in a 2004 issue of the journal "Population Studies." In their comment, the critics have argued that the cohort-fertility analysis in the aforesaid paper is weak on theoretical grounds and the empirical analysis is incomplete. The authors affirm that they agree with the comment that, as a society, the Netherlands differs from Southern Europe and even more from Central and Eastern Europe. Nevertheless, from a contemporary global perspective, these differences should not be overemphasized. They say that in their analyses, they used the Netherlands as a reference case of a country with an extraordinary pattern of late childbearing that is not associated with lowest-low fertility levels. However, the critics believe that these unusual characteristics invalidate the use of the Dutch example in the paper. So, this criticism is misconceived. It is precisely the unusualness of the fertility pattern in the Netherlands that makes it a useful reference point in the study of low and lowest-low fertility.

DeFries-Fulker (DF) Analysis for unselected populations is reformulated as a no-intercept model with centered variables and only two independent variables. The reformulation serves three purposes. First, the original formulation implicitly estimated two different values forc2 and two values forh2 . The new formulation resolves this ambiguity. Second, because the original formulation estimatedh2 with the coefficient from a regression-interaction term, whether to center the interaction variables was unclear. The new formulation explicitly resolves this issue. Finally, the new formulation estimates fewer parameters, and therefore improves estimation efficiency and statistical power. [ABSTRACT FROM AUTHOR]

We investigated the timing of fertility and marriage in Sweden using exogenous variation in the age at school graduation that results from differences in birth month. Our analysis found that the difference of 11 months in the age at leaving school between women who were born in two consecutive months, December and January, implies a delay in the age at first birth of 4.9 months. This effect of delayed graduation also persists for the timing of second births and first marriages, but it does not affect completed fertility or the overall probability of marriage before age 45. These results suggest the existence of a relatively rigid sequencing of demographic events in early adulthood, and the age at graduation from school emerges as an important factor in determining the timing--but not the quantum--of familyformation. In addition, these effects point to a potentially important influence of social age, defined by an individual's school cohort, instead of biological age. The relevance of social age is likely due to social interactions and peer-group influences exerted by individuals who are in the same school cohort but are not necessarily of the same age. [ABSTRACT FROM AUTHOR]

In this paper we conduct descriptive aggregate analyses to revisit the relationship of low and lowest-low period fertility to cohort fertility and key fertility-related behaviour such as leaving the parental home, marriage, and women's labour force participation. Our analyses show that the cross-country correlations in Europe between total fertility and the total first marriage rate, the proportion of extramarital births, and the labour force participation of women reversed during the period from 1975 to 1999. By the end of the 1990s there was also no longer evidence that divorce levels were negatively associated with fertility levels. We argue that lowest-low fertility has been particularly associated with a 'falling behind' of cohort fertility at higher birth orders and later ages. From these analyses we conclude that the emergence of lowest-low fertility during the 1990s was accompanied by a disruption or even a reversal of many well-known relationships that have been used to explain cross-country differences in fertility patterns. [ABSTRACT FROM AUTHOR]

Lowest-low fertility, defined as a period total fertility rate at or below 1.3, has rapidly spread in Europe during the 1990s. This article traces the emergence of this new phenomenon to the interaction of five factors. First, tempo and compositional distortions reduce the total fertility rate below the associated level of cohort fertility. Second, socioeconomic changes--including increased returns to human capital and high economic uncertainty in early adulthood--have made late childbearing a rational response for individuals and couples. Third, social interaction effects reinforce this behavioral adjustment and contribute to large and persistent postponement in the mean age at birth. Fourth, institutional settings favor an overall low quantum of fertility. Fifth, postponement-quantum interactions amplify the consequences of this institutional setting when combined with ongoing delays of childbearing. The article concludes with speculations about future trends in current and prospective lowest-low-fertility countries. [ABSTRACT FROM AUTHOR]

The impacts of social networks on changes in contraception in rural Kenya are investigated using special data from a longitudinal household survey. An analytic model, informed by detailed knowledge of the setting, yielded estimates that indicate that (1) social networks have substantial effects even after unobserved factors (e.g., homophily) that may determine social networks are controlled; (2) controlling for these unobserved factors may substantially alter the estimated effects of networks (these controls were not used in previous studies); (3) network effects are important for both men and women; and (4) network effects are nonlinear and asymmetric, suggesting that networks provide information primarily through social learning, rather than by exerting social influence. [ABSTRACT FROM AUTHOR]

Behaviors related to fertility constitute primary candidates for investigating the relevance of evolutionary influences and biological dispositions on contemporary human behaviors. Using female Danish twin cohorts born 1870–1968, we document important transformations in the relative contributions of “nurture” and “nature” to within‐cohort variations in early and complete fertility, and we point toward a systematic relation between the socioeconomic context of cohorts and the relevance of genetic and shared environmental factors. This transformation is most striking for early fertility where genetic factors strengthen over time and are consistent with up to 50 percent of the variation in early fertility in most recent cohorts. Understanding this emerging relevance of genetic factors is of central importance because early fertility constitutes an important determinant of complete fertility levels in low‐fertility societies, and because teenage motherhood and early childbearing are often associated with negative life‐cycle consequences. Moreover, our results emphasize the need for socially and contextually informed analyses of nature and nurture that allow both factors to influence human reproductive behavior over time. [ABSTRACT FROM PUBLISHER]

This paper uses the 1698 Slavonian census to illuminate features of social organization and productive activity of an eastern European population under the New Feudalism of the 17th century. In particular we investigate the ability of community or kinship networks to provide substitutes for missing markets in securities and production factors. It is found that kinship networks increase the efficiency of agricultural production by facilitating the exchange of oxen. This confirms contemporary reports that draft animals were the critical constraint to the expansion of agricultural output. We also find that kinship networks fail to reduce the variability of output through mutual harvest insurance. [ABSTRACT FROM AUTHOR]

In this paper we establish the asymptotic distribution of DeFries Fulker (1985) regression estimates for heritability and shared environmental influences with double-entry twin data. A simple formula to estimate the covariance matrix of the coefficients in DF-regressions is provided, and applications to simulated data and Danish twin data show that this method can substantially increase the statistical power of the analyses. We also provide an ‘efficient DF-analysis’ that yields more precise estimates when additional covariates are included among the explanatory variables. [ABSTRACT FROM AUTHOR]

Demographers have argued increasingly that social interaction is an important mechanism for understanding fertility behavior. Yet it is still quite uncertain whether social learning or social influence is the dominant mechanism through which social networks affect individuals' contraceptive decisions. In this paper we argue that these mechanisms can be distinguished by analyzing the density of the social network and its interaction with the proportion of contraceptive users among network partners. Our analyses indicate that social learning is most relevant with high market activity; in regions with only modest market activity, however, social influence is the dominant means by which social networks affect women's contraceptive use. [ABSTRACT FROM AUTHOR]

Behavior genetic designs and analysis can be used to address issues of central importance to demography. We use this methodology to document genetic influence on human fertility. Our data come from Danish twin pairs born from 1953 to 1959, measured on age at first attempt to get pregnant (FirstTry) and number of children (NumCh). Behavior genetic models were fitted using structural equation modeling and DF analysis. A consistent medium-level additive genetic influence was found for NumCh, equal across genders; a stronger genetic influence was identified for FirstTry, greater for females than for males. A bivariate analysis indicated significant shared genetic variance between NumCh and FirstTry. [ABSTRACT FROM AUTHOR]

Bongaarts and Feeney have recently proposed an adjusted total fertility rate to disentangle tempo effects from changes in the quantum of fertility. We propose an extension to the Bongaarts and Feeney formula that includes variance effects: that is, changes in the variance of the fertility schedule over time. If these variance effects are ignored, the mean age at birth and the adjusted total fertility rate are biased. We provide approximations for these biases, and we extend the TFR adjustment to fertility schedules with changing variance. We apply our method to the Swedish baby boom and bust, and show that variance effects are important for evaluating the relative contributions of tempo and quantum effects to the fertility change from 1985 to 1995. [ABSTRACT FROM AUTHOR]

This article presents a comment on an article which discussed a model of European age-specific fertility patterns using Hadwiger functions. The authors fit the functions to an array of European populations and, in order to interpret the parameters, show the high correlation between a and total fertility, c and mean age of the mother, and ab/c and the modal age specific fertility rate. The authors reflect the analytical relationship between the parameters of the Hadwiger function and the properties of such a function which are developed. As the authors conjectured, c is needed in the analytical mean age of the Hadwiger function, and the analytical total fertility is proportional to a. The analytical total fertility of Hadwiger functions can be obtained by integration over an interval, which requires the c parameter to be positive. In exploring the relationship between the modal age at childbearing and the Hadwiger parameters, the modal age was obtained by differentiating f(x) with respect to x and equaling to zero. The a parameter is just an intensity parameter which should not affect the modal age. The c parameter reflects mean age at childbearing, and that there should be a direct relationship between mean and modal ages.

Fluctuations in birth rates in developed countries have been considerably less regular than many explanatory theories suggest. This paper argues that social interaction, i.e., the dependence of individuals' fertility decisions on the fertility behavior of other population members, is relevant even in developed countries. A formal model for investigating the static and dynamic consequences of social interaction for fertility is developed, and its aggregate implications are tested using a Markov switching regression model. The findings show that social interaction can lead to fluctuations in birth rates that are swift and difficult to foresee, and that these fluctuations are likely to be asymmetric: spells of low fertility have a considerably higher persistence than spells of high fertility. The paper suggests that high birth rates are likely to be followed by spells of low fertility. Transitions from low to high fertility occur at a substantially lower rate than transitions in the opposite direction. [ABSTRACT FROM AUTHOR]

Binary and censored variables can lead to erroneous inferences about heritability in family studies if the dichotomous or censored nature of the dependent variable is not properly accounted for. The bivariate probit and tobit models proposed in this paper provide a unified approach to family studies with binary, ordered, and censored variables. Each model in this paper is derived from a similar latent-variable structure which can contain covariates that affect the expected value of the dependent variable, as well as genetic and shared environmental influences that lead to an association among related individuals. We apply the models to the fertility outcome and fertility motivations of Danish twins born 1953–1964 and find relevant genetic influences on the number of children as well as the desired timing of the first child. [ABSTRACT FROM AUTHOR]

This article investigates the fertility of Danish twins born during the periods 1870-1910 and 1953-64 in order to pursue two central questions for understanding human reproduction: Do genetic dispositions influence fertility and fertility-related behavior? Does the relevance of the "nature versus nurture" debate shift over time or with demographic regimes? The authors find that genetic influences on fertility exist, but that their relative magnitude and pattern are contingent on gender and on the socioeconomic environment experienced by cohorts. Among females born in 1880-90 and after 1955, about 30-50 percent of the variance in fertility is due to genetic influences; these influences are substantially smaller for earlier and for interim birth cohorts. Male fertility is generally subject to smaller genetic and larger shared-environment effects than female fertility. Because genetic effects are most prevalent in situations with deliberately controlled fertility and relatively egalitarian socioeconomic opportunities, the authors propose that the genetic dispositions affect primarily fertility behavior and motivations for having children. Analyses of fertility motivations, measured by age of first attempt to have a child, support this interpretation. [ABSTRACT FROM AUTHOR]

Analyzes the effect of hedonic migration decisions and regional amenities on industrial location, focusing on the geography of economic regions. Description of the theoretical model used to study the interdependence between migration, regional amenities and industrial location; Identification of three distinct location patterns; Explanation associated with patterns.

This article presents information about a study which focuses on the persistent diversity in contraceptive practices across communities, or social strata while focusing on a proposed model of learning in social networks for modern fertility control. Understanding contraceptive choice is essential for improving women's reproductive health and for providing effective family planning services. Markets for contraceptive information are frequently absent and media may fail to convey the complex set of ideas and procedures involved in the adoption of fertility control. Faced with this market failure, women make contraceptive decisions based on information from early adopters in their social networks. Results of the study suggests that regional diversity and social stratification in contraceptive practices arise due to informal communications, rather than in-depth discussions about fertility control. The information shared among network partners is limited and there is unobserved heterogeneity with respect to women's attributes and characteristics. The qualitative choice model used in this study, yields the prediction that the probability of a woman adopting modem contraception equals the proportion of number of users in her social network.

The sulfate-reducing bacteria Desulfobacterium autotrophicum. Desulfobulbus propionicus and Archaeoglobus fulgidus (VC-16) and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their Coβ-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used. The samples from the three sulfate-reducers were identified with Coα-[α-(5'-methylbenzimidazolyl)]-Coβcyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, ¹H- and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide). The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the coffins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions. [ABSTRACT FROM AUTHOR]

During the twentieth century, the global population has gone through unprecedented increases in economic and social development that coincided with substantial declines in human fertility and population growth rates. The negative association of fertility with economic and social development has therefore become one of the most solidly established and generally accepted empirical regularities in the social sciences. As a result of this close connection between development and fertility decline, more than half of the global population now lives in regions with below-replacement fertility (less than 2.1 children per woman). In many highly developed countries, the trend towards low fertility has also been deemed irreversible. Rapid population ageing, and in some cases the prospect of significant population decline, have therefore become a central socioeconomic concern and policy challenge. Here we show, using new cross-sectional and longitudinal analyses of the total fertility rate and the human development index (HDI), a fundamental change in the well-established negative relationship between fertility and development as the global population entered the twenty-first century. Although development continues to promote fertility decline at low and medium HDI levels, our analyses show that at advanced HDI levels, further development can reverse the declining trend in fertility. The previously negative development–fertility relationship has become J-shaped, with the HDI being positively associated with fertility among highly developed countries. This reversal of fertility decline as a result of continued economic and social development has the potential to slow the rates of population ageing, thereby ameliorating the social and economic problems that have been associated with the emergence and persistence of very low fertility. [ABSTRACT FROM AUTHOR]

Objective: This study evaluates whether community norms, caregiver beliefs, and adolescents' own beliefs and perceptions, focused on early marriage, predict adolescent marriage aspirations in a low‐income context. Background: The processes that contribute to adolescent marriage aspiration formation have received little attention in low‐income contexts, particularly sub‐Saharan Africa. Understanding how marriage aspirations are formed is important because they are associated with critical education and health outcomes. Method: Using data that links Malawian adolescents (N = 2089) with their caregivers (N = 1452), gender‐stratified ordered logistic regression models were used to examine key relationships. Results: Results show that community norms for youngest acceptable marriage age predict when boys want to marry, but there is no conclusive evidence that they predict when girls want to marry. This study also shows that adolescents who believe it is acceptable to marry at an early age are more likely to want to marry early themselves. Conclusion: Both community norms and adolescents' own beliefs are central to the formation of their marriage aspirations. Implications: This study recommends that programs incorporate adolescent beliefs and perceptions when designing child marriage interventions and measuring their impact. In addition, theory‐driven measurement of community norms is encouraged to better evaluate their impact on both marriage aspirations and marriage age. [ABSTRACT FROM AUTHOR]

Child marriage has adverse consequences for young girls. Cross-sectional research has highlighted several potential drivers of early marriage. We analyse drivers of child marriage using longitudinal data from rural Malawi, where rates of child marriage are among the highest in the world despite being illegal. Estimates from survival models show that 26% of girls in our sample marry before age 18. Importantly, girls report high decision-making autonomy vis-à-vis the decision to marry. We use multivariate Cox proportional hazard models to explore the role of 1) poverty and economic factors, 2) opportunity or alternatives to marriage, 3) social norms and attitudes, 4) knowledge of the law and 5) girls’ agency. Only three factors are consistently associated with child marriage. First, related to opportunities outside marriage, girls lagging in school at survey baseline have significantly higher rates of child marriage than their counterparts who were at or near grade level. Second, related to social norms, child marriage rates are significantly lower among respondents whose caregivers perceive that members of their community disapprove of child marriage. Third, knowledge of the law has a positive coefficient, a surprising result. These findings are aligned with the growing qualitative literature describing contexts where adolescent girls are more active agents in child marriages. [ABSTRACT FROM AUTHOR]

Individuals age at vastly different rates resulting in significant within‐population heterogeneity in health and aging outcomes. This diversity in health and aging trajectories has rarely been investigated among low‐income aging populations that have experienced substantial hardships throughout their lifecourses. Utilizing 2006–2019 data from the Malawi Longitudinal Study of Families and Health and estimating group‐based trajectory models, our analyses identified three distinct lifecourse health trajectories: (1) comparatively good initial mental and physical health that persisted throughout the lifecourse ("resilient aging"), (2) relatively good initial mental and physical health that started to deteriorate during mid‐adulthood ("accelerated aging"), and (3) poor initial mental and physical health that further declined over the lifecourse ("aging with persistently poor health"). For both physical and mental health, men were more likely to enjoy resilient aging than women. Predictors other than gender of trajectory membership sometimes confirmed, and sometimes contradicted, hypotheses derived from high‐income country studies. Our analyses highlight the long arm of early life conditions and gender in determining aging trajectories and show that a nontrivial subpopulation is characterized by aging with persistently poor health. The study uncovers widening gaps in health outcomes between those who age with resilience and those who experience accelerated aging. [ABSTRACT FROM AUTHOR]

Over a third of new HIV infections occur in adolescents aged 10–19 globally. Pre-exposure prophylaxis (PrEP) could be a powerful tool for prevention. Understanding more about the drivers of PrEP interest could inform implementation strategies among this age group. Moreover, family dynamics may play a uniquely critical role for this younger age group, thus it is important to gauge whether caregivers would support their children's use of PrEP. We surveyed 2,089 adolescents (aged 10–16) and their caregivers in Malawi during 2017–2018. Data were collected on PrEP interest, factors that may facilitate PrEP use, and preferences for PrEP modality. We used multivariate logistic regression to estimate the association between the above characteristics and PrEP interest. We find that young adolescents are engaging in behaviors that would put them at substantial risk of acquiring HIV, would likely benefit from PrEP, are largely (82%) interested in using such, would prefer to get an injection over taking a daily pill, and are considerably discouraged by the prospect of side effects. Endorsement by caregivers was even greater (87%). Our findings demonstrate initial support for adolescent PrEP, and suggest parents may be a surprising advocate. [ABSTRACT FROM AUTHOR]

Introduction: Childhood adversity is robustly associated with poor health across the life course. However, very few studies have examined the prevalence and implications of adverse childhood experiences in low- and middle-income countries. The objective of this study is to measure adverse childhood experiences among adolescents in Malawi and examine the association with mental and physical health outcomes.Methods: From 2017 to 2018, baseline data were collected among adolescents aged 10-16 years (n=2,089). Respondents were interviewed in their local language at their homes. Respondents completed questions on childhood adversity (Adverse Childhood Experiences-International Questionnaire), self-rated health, mortality expectations, and mental health (Beck Depression Inventory and Post-Traumatic Stress Disorder Scale). Stunting, obesity, and grip strength were measured. Analyses were conducted in 2018. Frequencies described the prevalence of adverse childhood experiences, and adjusted multivariate models examined whether cumulative adversity predicts current health.Results: Adolescents reported a high burden of adversity (i.e., 5 lifetime adverse childhood experiences on average). Adolescents who scored in the top adverse childhood experiences quintile were more likely to report depression (OR=3.11, 95% CI=2.10, 4.60), post-traumatic stress disorder (OR=4.19, 95% CI=2.43, 7.23), worse self-rated health (OR=3.72, 95% CI=2.03, 6.81), and a higher expected likelihood of dying in the next 5 years (RR=5.02, 95% CI=2.15, 7.88) compared with those in the bottom quintile. However, adverse childhood experiences did not demonstrate a graded relationship with obesity, stunting, or grip strength.Conclusions: These patterns are quite consistent with evidence from high-income countries and suggest that primary prevention of adverse childhood experiences should be a priority to ensure lifelong health in low-resources settings. [ABSTRACT FROM AUTHOR]