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Download rates of academic journals have joined citation rates as commonly-used indicators of the value of journal subscriptions.  While citation rates reflect worldwide influence, the value that a single library places on access to a journal is probably more accurately measured by the rate at which it is downloaded by local users.  If local download rates accurately measure local usage, there is a strong case for employing download rates to compare the cost-effectiveness of journals. We examine download data for more than five thousand journals subscribed to by the ten universities in the University of California system. We find that controlling for measured journal characteristics - citation rates, number of articles, and year of download - download rates, as captured by the ratio of downloads to citations, differs substantially between academic disciplines. This suggests that discipline specific adjustments to download rates are needed to construct a reliable tool for estimating local usage. Even after adding academic disciplines to the variables we control for, we find that there remain substantial ``publisher effects'', with some publishers recording significantly more downloads than would be predicted by the characteristics of their journals. While the usage tool can be modified to incorporate the publisher effect, this raises the question of what causes such substantial differences across publishers once journal and discipline characteristics are accounted for.

This paper extends the classic Volunteer’s Dilemma game to environments in which individuals have differing costs and private information about their own costs. It exploresthe nature of symmetric ethical optimum strategies for Volunteer's Dilemma games with and without differing costs. Where costs differ, ethical optima are constructed by symmetrizing the game with a Rawlsian “Veil of Ignorance

Download rates of academic journals have joined citation rates as commonly used measures of research influence. But in what ways and to what extent do the two measures differ? This paper examines six years of download data for more than five thousand journals subscribed to by the University of California system. While down- load rates of journals are highly correlated with citation rates, the average ratio of downloads to citations varies substantially among academic disciplines. We find that, typically, the ratio of a journal’s downloads to citations depends positively on its im- pact factor. Surprisingly, we find that, controlling for citation rates, number of articles, academic discipline and year of download, there remains a “publisher effect,” with some publishers recording significantly more downloads than would be predicted from char- acteristics of their journals. Download statistics are recorded and supplied to libraries by journal publishers, often subject to confidentiality clauses. If libraries use download statistics to evaluate journals, they may want to account for publisher bias in these statistics.

The plight of multiracial leukemia patients who are unable to find matching stem cell donors has received much media attention. These news stories, while dramatic, are short on statistical information and long on misconceptions. We apply simple probability theory, the genetics of sexual diploid reproduction, and the theory of public goods to produce estimates of the probabilities that multiracial patients will find matching donors in the existing registry. We then compute the benefits and costs of registering more potential donors of single and mixed races. c

Students in a large principles class participated in a market experiment in which they had opportunities to take entrepreneurial action. These students had also taken the Meyers-Briggs personality test. We explore the relation between personality characteristics and participation decisions.

Limited time and budgets have created a legitimate need for quantitative measures of scholarly work. The well-known journal impact factor is the leading measure of this sort; here we describe an alternative approach based on the full structure of the scholarly citation network. The Eigenfactor and Article Influence Score use an iterative ranking scheme similar to Google's PageRank algorithm. With this approach, citations from top journals are weighted more heavily than citations from lower-tier publications. We describe these metrics and the rankings that they provide.

A recent article by Phil Davis suggested that the Eigenvalue metric does adds little useful information to the more simply calculated measure of total citations published by the ISI. This paper argues that Davis's claim is an instance of a classic statistical fallacy of spurious correlation. Based on an analysis of the entire 2006 ISI Journal Citation Reports, we show that there are statistically and economically significant differences between the Eigenfactor metrics and the ISI's impact factor and total citations.

This article was written in celebration of Eleanor Ostrom's Nobel Prize. Standard economic approaches to the problem of overuse of common property resources have emphasized two competing remedies, the Pigovian approach of corrective taxation and the property rights approach of internalizing externalities by means of assigning marketable property rights to individual owners with exclusive claim on the entire commons. Elinor Ostrom pursues a third approach, which is based on case studies of existing communities that have established successful and durable systems of managing common property resources. This paper discusses her work and suggests that economists with an interest in public policy have much to gain from becoming familiar with the work of Ostrom and her co-authors.

We provide simple formulas that can be used to calculate ideal bootstrap or exact recombination estimates of group statistics from experimental data.

This paper studies a general class of pure exchange economies that have multiple equilibria, which extend an example presented by Lloyd Shapley and Martin Shubik. For such economies, we find easily verified conditions that determine whether there are multiple equilibria. We also provide simple methods for constructing economies in which arbitrary pre-specified sets of prices are equilibria. These economies have simple comparative statics, since prices at interior competitive equilibrium depend on the parameters of utility but not on the endowment quantities.

The impact factor of an academic journal for any year is the number of times the average article published in that journal in the previous two years are cited in that year. From 1994-2005, the average impact factor of journals listed by the ISI has been increasing by an average of 2.6 percent per year. This paper documents this growth and explores its causes.

Transplants of donated stem cells save the lives of many patients with blood diseases. Donation is somewhat painful, but rarely has lasting adverse effects. Patients can accept transplants only from donors with compatible immune systems. Those lacking a sibling match must seek donations from the population at large. The probability that two persons of the same race are compatible is less than 1/10,000. Health authorities maintain a registry of several million genetically-tested potential donors who have agreed to donate if asked. We study the peculiar structure of voluntary public good provision represented by the registry, and compare the marginal benefits and marginal costs of expanding the registry.

This paper describes techniques that I use to teach economics principles "interactively". These techniques include classroom experiments and classroom clickers. The paper describes an experiment on market entry and gives examples of applications of classroom clickers. Clicker applications include the collection data about student preferences that can be used to construct demand curves and supply curves. Check on students' knowledge of central concepts. Play interactive games that illustrate economic concepts.

The article focuses on the economics of family partnerships. It states an allegory involving a prehistoric couple who split their responsibilities of gathering food and building a fire to create econometric models for family behavior. In theory, monogamous couples have exactly the same interest in their reproductive success, hence completely shared interest in their children. This is not the case in practice, as a variety of marital problems, divorce, and remarriage adversely affect the equation. The observed fact that an increase in a society's wealth tends to decrease family size runs counter to evolutionary biologic theory. No one theory in economics or biology has an adequate explanation for the reduction in family size as wealth increases. A variety of outside factors, notably the decline in child mortality and the change from an agricultural to an urban society, affect the models in both disciplines.

To answer the question of the paper's title, we looked at the tables of contents from two recent issues of 33 economics journals and attempted to find a freely available online version of each article. We found that about 90 percent of articles in the most-cited economics journals and about 50 percent of articles in less-cited journals are available. We conduct a similar exercise for political science and find that only about 30 percent of the articles are freely available. The paper reports a regression analysis of the effects of author and article characteristics on likelihood of posing and it discusses the implications of self-archiving for the pricing of subscription-based academic journals.

How should benefit-cost analysis account for the value that benevolent individuals place on other people's pleasure from public goods? When adding up the benefits to be compared with costs, should we sum the private valuations, the altruistic valuations, or something else? This paper proposes a partial answer and offers some suggestions for benefit-cost practitioners.

In many applications,assumptions about the log-concavity of a probability distribution allow just enough special structure to yield a workable theory.This paper catalogs a series of theorems relating log-concavity and/or log-convexity of probability density functions,distribution functions,reliability functions,and their integrals. We list a large number of commonly-used probability distributions and report the log-concavity or log-convexity of their density functions and their integrals.We also discuss a variety of applications of log-concavity that have appeared in the literature.

The net present value of costs and benefits from a pay-as-you-go social security system are negative for young people and positive for the elderly. If people all vote their financial self-interest, there will be a pivotal age such that those who are younger favor smaller social security benefits and those who are older will favor larger benefits. For persons of each age and sex, we estimate the expected present value gained or lost from a small permanent increase in the amount of benefits, where the cost of these benefits is divided equally among the population of working age. Assuming that everyone votes his or her long run financial self-interest, and calculating the number of voters in the population of each age and sex, we can determine whether there is majority support for an increase or a decrease in social security benefits. We use statistics on the age distribution and mortality rates for the United States to explore the sensitivity of political support for social security to alternative assumptions about the discount rate, excess burden in taxation, voter participation rates, and birth, death, and migration rates. We find that a once-and-for-all decrease in benefits would be defeated by a majority of selfish voters under a wide range of parameters. We also study the predicted majority outcomes of votes on changing the retirement age.

Edward Chamberlin, who initiated classroom market experiences, used the results of his experiments to argue that competitive equilibrium performs poorly in explaining the outcomes of real markets. Vernon Smith altered the design of Chamberlin's experiment so as to increase the amount of price information available to traders and in classroom experiments with this design found that trading outcomes were close to those predicted by competitive theory. This paper examines results of classroom trading experiments using the design found in Experiments with Economic Principles, an introductory economics text by Ted Bergstrom and John Miller. The procedure in this experiment is intermediate between that of Chamberlin and that of Smith. We have collected data on transaction prices and quantities from a large number of classroom experiments using this design. We compare the experimental outcomes with the predictions made by competitive equilibrium theory and by a simple profit-splitting theory. Evidence suggests that neither theory is entirely successful, though in the first rounds of trading there seems to be a significant amount of profit-splitting and as traders become more experienced, outcomes are closer to those predicted by competitive theory.

Edward Chamberlin conjectured that the number of trades in realistic trading systems is likely to exceed that predicted by competitive equilibrium theory. He supported this conjecture by data from a large number of classroom experiments and with a plausible argument based on a numerical example. This paper states and proves a theorem that supports and illuminates Chamberlin's intuition, supplies examples of trading processes that lead to excess trading, and presents some additional experimental evidence.

Scientific publishing is rapidly shifting from a paper-based system to one of predominantly electronic distribution, in which universities purchase site licenses for online access to journal contents. Will these changes necessarily benefit the scientific community? By using basic microeconomics and elementary statistical theory, we address this question and find a surprising answer. If a journal is priced to maximize the publisher’s profits, scholars on average are likely to be worse off when universities purchase site licenses than they would be if access were by individual subscriptions only. However, site licenses are not always disadvantageous. Journals issued by professional societies and university presses are often priced so as to maximize subscriptions while recovering average costs. When such journals are sustained by institutional site licenses, the net benefits to the scientific community are larger than if these journals are sold only by individual subscriptions.

Scientific publishing is rapidly shifting from a paper-based system to one of predominantly electronic distribution, in which universities purchase site licenses for online access to journal contents. Will these changes necessarily benefit the scientific community? By using basic microeconomics and elementary statistical theory, we address this question and find a surprising answer. If a journal is priced to maximize the publisher s profits, scholars on average are likely to be worse off when universities purchase site licenses than they would be if access were by individual subscriptions only. However, site licenses are not always disadvantageous. Journals issued by professional societies and university presses are often priced so as to maximize subscriptions while recovering average costs. When such journals are sustained by institutional site licenses, the net benefits to the scientific community are larger than if these journals are sold only by individual subscriptions.

In many applications, assumptions about the log-concavity of a probability distribution allow just enough special structure to yield a workable theory. This paper catalogs a series of theorems relating log-concavity and/or log-convexity of probability density functions, distribution functions,reliability functions, and their integrals. We list a large number of commonly-used probability distributions and report the log-concavity or log-convexity of their density functions and their integrals. We also discuss a variety of applications of log-concavity that have appeared in the literature.

This paper explores the way that assortative matching can maintain cooperative behavior under evolutionary dynamics.

The paper generalizes theorems of Ky Fan and Hugo Sonnenschein on the existence of maximal elements for non-transitive relations. I used these results to show that a binary relation could be constructed whose maximal element must be a competitive equilibrium. Thus proving the existence of competitive equilibrium under somewhat more general conditions than had been done previously. In 1975, I thought this was a useful extension of the Gale Mas Collel existence theorem. Journal referees then didn't agree with me, so I let it ripen in my desk for 15 years. I still think it is worth looking at if you are interested in the existence of competitive equilibrium or in maximization of funny preference orderings.

Alexander Field was not convinced of a result that I claimed in my JEP 2001 paper that in "haystack models" with non-assortative mating, if the number of descendants of founding group members is determined by an n-player prisoners' dilemma game, then the population will converge to a population of defectors. He thought that the result applied only if the groups were large. I respond with a more detailed discussion and show how the result works even when groups have only two members.

A retrospective on Vernon Smith's contributions to experimental economics, written for the Scandinavian Journal of Economics.