Search

The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to other large fusion experiments, W7-X has a relatively low power-to-volume ratio. However high heating power is particularly necessary for achieving high plasma beta values, where the improved confinement of fast ions, one of the optimization criteria of W7-X, can be examined. It is therefore necessary to expand the ECRH systems in several consecutive steps. It is planned to increase the number of gyrotron positions from 10 to 12 and at the same time to evolve the gyrotron output power in several development steps from 1 MW to nominal 1.5 MW and, finally, up to 2 MW. At the same time, the transmission lines will also be upgraded for 2 MW operation. A special effort is also made to improve the reliability of the system by the fast control system.

For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equipped with a steady-state capable ECRH system, operating at 140 GHz, which corresponds to the 2nd cyclotron harmonic of the electrons at a magnetic field of 2.5 T. Ten gyrotrons are operational and already delivered 7 MW to W7-X plasmas. Combined with pellet injection, the highest triple product (0.68 ×1020 keV m-3 s), observed up to now in stellarators, was achieved (Sunn Pedersen et al 2018 Plasma Phys. Control. Fusion 61 014035). For the first time, W7-X plasmas were sustained by 2nd harmonic O-mode heating, approaching the collisionality regime for which W7-X was optimized. Power deposition scans did not show any indication of electron temperature profile resilience. In low-density, low-power plasmas a compensation of the bootstrap current with electron-cyclotron current drive (ECCD) was demonstrated. Sufficiently strong ECCD close to the plasma centre produced periodic internal plasma-crash events, which coincide with the appearance of low order rationals of the rotational transform.

Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good confinement is realized, and that the measured deviations are smaller than one part in 100,000. This is a significant step forward in stellarator research, since it shows that the complicated and delicate magnetic topology can be created and verified with the required accuracy., Early stellarator designs suffered from high particle losses, an issue that can be addressed by optimization of the coils. Here the authors measure the magnetic field lines in the Wendelstein 7-X stellarator, confirming that the complicated design of the superconducting coils has been realized successfully.

This paper reports on a randomized field experiment in which first-year university students could earn financial rewards for passing all first-year requirements within one year. Financial incentives turn out to have positive effects on achievement of high-ability students, whereas they have a negative impact on achievement of low-ability students. After three years these effects have increased, suggesting dynamic spillovers. The negative effects for less-able students are consistent with results from psychology and behavioral economics showing that external rewards may be detrimental for intrinsic motivation.

Advocates of increased school choice and competition assume that school choices are led by quality considerations. To test this assumption, this paper examines the determinants of secondary school choice in the city of Amsterdam. In this city there are many schools to choose from and school choice is virtually unrestricted (no catchment areas, low or no tuition fees, short distances). Using discrete choice models we find that published indicators of school quality are not consistent predictors of school choice. Instead, students appear to prefer schools that are close to their home and schools where many of their former classmates in primary school go to.

De hoge inkomens van medisch specialisten zijn voor een belangrijk deel het resultaat van de kunstmatige schaarste aan artsen in Nederland. Die is ontstaan door het van overheidswege limiteren van het aantal studenten dat geneeskunde kan studeren (numerus fixus). Dit stellen Nadine Ketel, Bas van der Klaauw, Edwin Leuven en Hessel Oosterbeek op basis van een onderzoek naar de beloning van medisch specialisten en huisartsen. Medisch specialisten moeten weliswaar relatief lang studeren, maar het extra inkomen dat zij later verdienen is veel hoger dan de misgelopen inkomsten tijdens de lange studie. De overheid kan dit profiteren van kunstmatige schaarste corrigeren door bijvoorbeeld het collegegeld voor geneeskundestudenten fors te verhogen of de studenten zelf te laten betalen voor hun specialisatie.

We estimate the returns to medical school by exploiting that admittance to medical school in the Netherlands is determined by a lottery. Using data from up to 21 years after the lottery, we find that doctors earn at least 20 percent more than people who end up in their next-best occupation. Estimated earnings profiles suggest that the life-time difference is even much larger: 21 years after the lottery the earnings difference exceeds 60 percent. Only a small fraction of this difference can be attributed to differences in working hours and human capital investments. The returns do not vary with gender or ability, but are higher for the less motivated.

De grote daling in het aanbod van scholen als gevolg van een stijging in de opheffings-normen in 1994 heeft een positief effect gehad op leerprestaties in het primair onderwijs. Dit resultaat kan verklaard kan worden door schaalvoordelen die de effecten van minder schoolkeuze en competitie domineerden.

Using a difference-in-differences framework, we estimate the impact of Ramadan on educational outcomes of Muslim students living in a non-Muslim country. For identification we exploit the fact that the number of Ramadan weeks during the course that we study, varies from year to year, ranging from zero to four. Our main finding is that Ramadan observance has a negative impact on performance; one additional Ramadan week lowers the final grade of Muslim students by almost ten percent of a standard deviation.

This paper investigates whether studying abroad increases the propensity to live abroad later on. We use an instrumental variable approach based on cut-offs in the ranking of Dutch higher education graduates who applied for a scholarship programme for outstanding students. Applicants ranked above the cut-off received a scholarship to study abroad. Applicants ranked below the cut-off were denied a scholarship. Assignment of a scholarship increases the probability to study abroad and the number of months spent studying abroad. Studying abroad and the number of months spent studying abroad increase the probability of currently living abroad.

This paper presents estimates of the general equilibrium effect of school choice and competition on achievement of primary school pupils in the Netherlands. For identification we exploit a change in the rule that determines schools' minimum required size. Before the change this size was a step-function of municipalities' number of inhabitants. After the change it is a concave function of pupil density in a municipality. On average the number of schools decreased by 15 percent, but this varied considerably across municipalities. We find that reducing the number of schools by 10 percent increases pupils' achievement by 3 percent of a standard deviation. In the Dutch system with free choice, a reduction in the supply of schools not only implies a reduction in school choice but, for a given number of pupils, also implies an increase in average school size. We present evidence that supports the hypothesis that in our context, scale economies dominated the effects of choice and competition. This result points to an often ignored trade-off between the benefits of choice and competition and the benefits of scale economies.

This chapter surveys the economics literature on overeducation. The original motivation to study this topic reports that the strong increase in the number of college graduates in the early 1970s in the United States led to a decrease in the returns to college education. We argue that Duncan and Hoffman's augmented wage equation—the workhorse model in the overeducation literature—in which wages are regressed on years of overschooling, years of required schooling, and years of underschooling is at best loosely related to this original motivation. Next, we discuss how overschooling and underschooling at the level of individual workers have been measured, and what the incidence of overschooling and underschooling is. We then analyze in more detail Duncan and Hoffman's wage equation. We discuss the potential problems with it due to endogeneity and measurement error, and we review the results from earlier studies using this specification. We conclude that because of the issues concerning endogeneity and measurement error, the estimated returns to required/under/overschooling cannot be interpreted as causal.

To raise school attendance, many programs in developing countries eliminate or reduce private contributions to education. This paper documents an unintended negative effect of such programs. Using data from a randomized experiment that provides free uniforms to primary school children in Ecuador, we find that the intervention has a significantly negative impact on attendance. An explanation is that parents who pay for their children’s uniforms (the control group) feel more committed to the school than parents who got the uniforms for free (the treated) and therefore encourage their children to attend school. Consistent with this sunk cost effect, we find that the impact is largest shortly after the purchase of the uniform, and during the end-of-year exam period when more is at stake.

In this paper we investigate how heterogeneous agents choose among tournaments with different prizes. We show that if the number of agents is sufficiently small, multiple equilibria can arise. Depending on how the prize money is split over the tournaments, these may include, for example, a perfect-sorting equilibrium in which high-ability agents compete in the highprize tournament, while low-ability agents compete for the low prize. However, there are also equilibria in which agents follow a mixed strategy and there can be reverse sorting, i.e. low-ability agents are in the tournament with the high prize, while high-ability agents are in the low-prize tournament. We show that total effort always decreases compared to a single tournament. However, splitting the tournament may increase the effort of low-ability agents

Recent studies for primary and secondary education find positive effects of the share of girls in the classroom on achievement of boys and girls. This study examines whether these results can be extrapolated to post-secondary education. We conduct an experiment in which the shares of girls in workgroups for first year students in economics and business are manipulated and students are randomly assigned to these groups. Boys tend to postpone their dropout decision when surrounded by more girls, and there is also a modest reduction in early absenteeism. On the other hand, boys perform worse on courses with high math content when assigned to a group with many girls. Overall, however, we fail to find substantial gender peer effects on achievement. This in spite of the fact that students' perceptions of the behavior of themselves and their peers are influenced by the share of girls.

A vast body of empirical studies lends support to the incentive effects of rankorder tournaments. Evidence comes from experiments in laboratories and non-experimental studies exploiting sports or firm data. Selection of competitors across tournaments may bias these non-experimental studies, whereas short task duration or lack of distracters may limit the external validity of results obtained in lab experiments or from sports data. To address these concerns we conducted a field experiment where students selected themselves into tournaments with different prizes. Within each tournament the best performing student on the final exam of a standard introductory microeconomics course could win a substantial financial reward. A standard non-experimental analysis exploiting across tournament variation in reward size and competitiveness confirms earlier findings. We find however no evidence for effects of tournament participation on study effort and exam results when we exploit our experimental design, indicating that the non-experimental results are completely due to sorting. Treatment only affects attendance of the first workgroup meeting following the announcement of treatment status, suggesting a difference between short-run and long-run decision making.

This paper describes and analyzes different financial schemes to promote lifelong learning. Positive effects of financial incentives to pupils are not restricted to high ability pupils, as low ability students also seem to benefit. The evidence regarding the effects of subsidy forms is limited. The most prominent knowledge gaps regarding the effects of various financing schemes related to lifelong learning are the effects of vouchers; financial aid schemes for students; and entitlements and individual learning accounts.

This paper examines the wage premium to computer use in a developing country: Ecuador. We use different approaches to establish whether the premium is causal. Controlling for a large set of observables we find a wage difference between users and non-users of around 27%. Using first differences, the premium reduces to around 10%. We find however, no effect of the number of hours of computer use on wages. Moreover, the premium to using pencils is very similar to the computer premium. Groups that earn a higher computer premium also earn a higher pencil premium, and the penalty/gain for losing/winning a computer are almost identical to the penalty/gain of losing/gaining pencils. Taken together, these findings suggest that also in this developing country the computer premium does not reflect a causal impact of computers on productivity, but should be attributed to unobserved worker and/or job characteristics. JEL-codes: Keywords: Computers, wage inequality, developing country, Ecuador

This paper analyzes the impact of a leading entrepreneurship education program on students’ entrepreneurship competencies and intentions using an instrumental variables approach in a difference-in-differences framework. We exploit that the program was offered to students at one location of a school but was not offered to students at another location of the same school. Location choice (and thereby treatment) is instrumented by the relative distance of locations to parents’ place of residence. The results show that the program does not have the intended effects: the effect on students’ self-assessed entrepreneurial skills is insignificant and the effect on the intention to become an entrepreneur is even significantly negative.

Policies need not only to be well designed to effectively address market failures, but their parameters also need to be part of agents' information sets. This is illustrated by government student loans in the Netherlands which are intended to alleviate liquidity constraints. Despite generous loan conditions, take-up rates on these loans are low. Some have argued that this is due to limited knowledge about these conditions. We examine the importance of information constraints through a randomized experiment. Half of the students who responded to an Internet questionnaire were given factual information on loan conditions, whereas the other half did not receive such information. Six months later, students who received information have better knowledge about the loan conditions. While OLS regressions reveal a large and significantly positive association between knowledge about loan conditions and borrowing, our instrumental variable estimates suggest that this is not a causal effect which would rule out that the low take-up rate is caused by information constraints. Policies need not only to be well designed to effectively address market failures, but their parameters also need to be part of agents' information sets. We study student loan behavior in the Netherlands where i) higher education students know little about the conditions of the government's financial aid program and ii) take-up rates are low. We conducted a field experiment in which we manipulated the amount of information students have about these conditions. Half a year after the treatment the same students were interviewed again. The treatment has no impact on loan take-up. This zero impact is not due to students already having decided whether to take a loan or not, and can also not be attributed to treated students not absorbing the information that is given to them. We provide the interpretation that communicating eligibility criteria rather than precise programme details should be prioritized.

In 2007 the government of Ecuador launched a micro-credit program for enterprises run by poor households. The program was targeted to households at the bottom two quintiles in the wealth distribution. This paper uses data collected prior to the start of the program to examine whether the government's targeting strategy reaches all households that are constrained in their access to loans of the type provided by the program. We nd that the program excludes households in the third quintile of the wealth distribution that are equally credit constrained and have very similar demands for credit as households served by the program.

This paper presents evidence about the impact on school enrollment of a program in Ecuador that gives cash transfers to the 40 percent poorest families. The evaluation design consists of a randomized experiment for families around the first quintile of the poverty index and of a regression discontinuity design for families around the second quintile of this index, which is the program’s eligibility threshold. This allows us to compare results from two different credible identification methods, and to investigate whether the impact varies with families’ poverty level. Around the first quintile of the poverty index the impact is positive while it is equal to zero around the second quintile. This suggests that for the poorest families the program lifts a credit constraint while this is not the case for families close to the eligibility threshold.

This paper estimates the effects of attending medical school on health behavior and health status exploiting that admission to medical school in the Netherlands is determined by a lottery. Because lottery losers are permitted to re-apply, we use the result of the first lottery in which someone participates as instrumental variable. Our results show that health education reduces alcohol intake and being underweight, and seems to reduce smoking. It has, however, no impact on being overweight or obese, or on subjective health status. The effect on the frequency of physical exercise is even negative. This mixed evidence makes it unlikely that the content of education programs explains the education gradient for health. Health education has a large impact on the probability of being registered for donations of organs, suggesting that information provision is a possible channel to raise the supply of organs

A vast body of empirical studies lends support to the incentive effects of rank-order tournaments. Direct evidence comes from experiments in laboratories or from non-experimental sports events (golf, tennis). The short duration of the tasks at hand or the lack of distractors may limit the external validity of the findings from these studies. Moreover, non-experimental results can be biased due to self-selection. To address these concerns we conducted a field experiment where the best performing student on the final exam of a standard introductory micreconomics course could win a substantial financial reward. A standard non-experimental analysis confirms earlier findings. We find however no evidence of effects of treatment on effort or productivity when we exploit our experimental design. The only exception is that treatment has a significant impact on attendance of the first workgroup meeting immediately after the announcement of treatment status, suggesting a difference between short run and long run decision making.

To stimulate investment in training by individuals, the Dutch tax system allows a deduction of direct training expenditures from taxable income. This paper investigates to what extent the resulting cost reduction encourages training investments. Two different identification strategies are used. The first strategy uses the progressive structure of the income tax scheme and compares groups with taxable income just above or just below kinks. The second strategy takes advantage of the 2001 tax reform, which implied substantial changes in marginal tax rates. These strategies exploit different sources of exogenous variation and are based on different identifying assumptions. Nevertheless, the results point in the same direction: tax incentives increase training participation.

Velen zien onderwijs en kennis als belangrijke pijlers van de economie. Maar waar duidelijk lijkt dat kennis en onderwijs belangrijk zijn voor de economische ontwikkeling van een land, is minder evident hoe extra investeringen concreet zouden moeten worden ingezet. Dit komt doordat van veel maatregelen de effectiviteit onbekend is. Dat geldt ook voor maatregelen die zijn gericht op bevordering van de deelname aan scholing, zoals de fiscale aftrek scholingsuitgaven. In dit rapport wordt het effect van de fiscale aftrek scholingsuitgaven onderzocht. Het onderzoek is verricht door onderzoekers van de SEO Economisch Onderzoek en Scholar, twee onderzoeksinstituten van de Universiteit van Amsterdam, in opdracht van de Ministeries van Financiën, SZW en OCW. In dit rapport staan de volgende onderzoeksvragen centraal: 1. Wat is het feitelijke gebruik van de aftrek scholingsuitgaven? 2. Wat is het effect van de aftrek scholingsuitgaven op scholingsdeelname?

Until 1975 lower vocational education in the Netherlands had a program length of either 3 or 4 years. In 1975 all 3 year programs were extended to 4 years. This was accompanied by an increase of the compulsory school leaving age with one year. We evaluate the long-term wage of effects of the extra year of lower vocational education using a difference-in-differences approach. We find no beneficial effects from the change.

This study estimates the effect of expanding enrollment possibilities in early eduction on the achievement of young children. To do so it exploits two features of the Dutch schooling system. First, children are allowed to enroll in school on their fourth birthday. Second, children having their birthday before, during and after the summer holiday are placed in the same class. Together these features generate sufficient exogenous variation in children s potential time in school to identify its effects on test scores. We find that allowing disadvantaged pupils to start school one month earlier increases their test scores on average by 0.06 of a standard deviation. This effect is of the same magnitude for pupils with lower educated parents and for minority pupils. For non- disadvantaged pupils we find no effect. Results are similar for language and math scores.

Breach penalties can be used to protect specific investments and are therefore a remedy against holdup. Not all breach remedies are, however, equally efficient. Some common types are predicted to protect too well thereby inducing overinvestment. Theoretically overinvestment is driven by two motives: the insurance motive and the separation prevention motive. This paper presents results from an experiment designed to test the effect of different breach remedies on specific investments in a setting where ex post renegotiations are possible. In line with other experimental studies we find that actual investment levels tend to exceed the predicted levels somewhat. Nevertheless the results provide ample support for the theory: investment levels under the different remedies vary in accordance with the theoretical predictions. More specifically, where predicted the insurance motive and the separation prevention motive are indeed at work.

Economic theory predicts that holdup may be alleviated by making the specific investment unobservable to the non-investor; private information creates an informational rent that boosts investment incentives. Experimental findings, however, indicate that holdup is attenuated by positive reciprocity. Private information may interfere with this, for instance when it becomes impossible to directly observe whether the investor behaved 'kindly' or not. In that way unobservability could weaken the reciprocity mechanism. This paper reports about an experiment to investigate this issue empirically. Our results are in line with standard theoretical predictions when there is limited scope for reciprocity. But with suffcient scope for reciprocity, unobservability does not boost specific investments.

This paper proposes a new approach to identify the wage effects of training. The idea is to narrow down the comparison group by only taking into consideration the workers who wanted to participate in training but did not do so because of some random event. The point estimate of the return to training consistently drops when restricting the comparison group this way. While the OLS estimate of the return to training participation is significantly positive, this is no longer the case when we use the new comparison group. This outcome suggests that a large share of what is usually interpreted as returns to training is actually the return to some unobservable characteristic.