Knowledge that Transforms

In many Asian countries the ratio of male to female population is higher than in the West: as high as 1.07 in China and India, and even higher in Pakistan. A number of authors (most notably Amartya Sen) have suggested that this imbalance reflects excess female mortality and have argued that as many as 100 million women are “missing.” This paper proposes an explanation for some of the observed overrepresentation of men: the hepatitis B virus. I present new evidence, consistent with an existing scientific literature, that carriers of the hepatitis B virus have offspring sex ratios around 1.50 boys for each girl. This evidence includes both cross‐country analyses and a natural experiment based on recent vaccination campaigns. Hepatitis B is common in many Asian countries, especially China, where some 10–15 percent of the population is infected. Using data on prevalence of the virus by country and estimates of the effect of hepatitis on the sex ratio, I argue that hepatitis B can account for about 45 percent of the “missing women”: around 75 percent in China, between 20 and 50 percent in Egypt and western Asia, and under 20 percent in India, Bangladesh, Pakistan, and Nepal.

We examine an economy whose consumers have different discount factors for utility, possibly not exponential. We characterize the properties of efficient allocations of resources and of the shadow prices that would decentralize such allocations. We show in particular that the representative agent has a decreasing discount rate when, as is usually posited, all of a group’s members have a constant discount rate and decreasing absolute risk aversion preferences. We also identify conditions that lead the representative agent to have a rate of impatience that decreases with gross domestic product per capita.

Bond yields respond to policy decisions by the Federal Reserve and vice versa. To learn about these responses, I model a high‐frequency policy rule based on yield curve information and an arbitrage‐free bond market. In continuous time, the Fed's target is a pure jump process. Jump intensities depend on the state of the economy and the meeting calendar of the Federal Open Market Committee. The model has closed‐form solutions for yields as functions of a few state variables. Introducing monetary policy helps to match the whole yield curve, because the target is an observable state variable that pins down its short end and introduces important seasonalities around FOMC meetings. The volatility of yields is "snake shaped," which the model explains with policy inertia. The policy rule crucially depends on the two‐year yield and describes Fed policy better than Taylor rules.

Sub‐Saharan Africa has a high incidence of polygyny. It is also the poorest region of the world. In this paper I ask whether banning polygyny could play any role for development. Using a quantitative model of polygyny, I find that enforcing monogamy lowers fertility, shrinks the spousal age gap, and reverses the direction of marriage payments. Polygyny leads to high bride‐prices to “ration” women, which makes buying wives and selling daughters a good investment, thus crowding out investment in physical assets. For reasonable parameter values, I find that banning polygyny decreases fertility by 40 percent, increases savings by 70 percent, and increases output per capita by 170 percent.

We extend the collective model of household behavior to allow for the existence of public consumption. We show how this model allows the analysis of welfare consequences of policies aimed at changing the distribution of power within the household. Our setting provides a conceptual framework for addressing issues linked to the “targeting” of specific benefits or taxes. We also show that the observation of the labor supplies and the household demand for the public good allow one to identify individual welfare and the decision process. This requires either a separability assumption or the presence of a distribution factor.

This article presents a two‐period asymmetric learning model of insurance markets. When information about past accidents is not shared by insurers, asymmetries of information develop through time. Equilibrium contracts exist, are payoff unique, and display a realistic bonus‐malus pattern. Eliminating asymmetries through information sharing is welfare decreasing, in contrast with past contributions on insurance and adverse selection. When second‐period contract offers cannot be contingent on initial contract choice, a strict increase in welfare is obtained through menus of contracts, although initial contract choice is in itself worthless information.

Fundamental tax reform is examined in an overlapping‐generations model in which heterogeneous agents face idiosyncratic wage shocks and longevity uncertainty. A progressive income tax is replaced with a flat consumption tax. If idiosyncratic wage shocks are insurable (i.e., no risk), this reform improves (interim) efficiency, a result consistent with the previous literature. But if, more realistically, wage shocks are uninsurable, this reform reduces efficiency, even though national wealth and output increase over the entire transition path. This efficiency loss, in large part, stems from reduced intragenerational risk sharing that was previously provided by the progressive tax system.

We show that standard winner‐pay auctions are inept fund‐raising mechanisms because of the positive externality bidders forgo if they top another’s high bid. Revenues are suppressed as a result and remain finite even when bidders value a dollar donated the same as a dollar kept. This problem does not occur in lotteries and all‐pay auctions, where bidders pay irrespective of whether they win. We introduce a general class of all‐pay auctions, rank their revenues, and illustrate how they dominate lotteries and winner‐pay formats. The optimal fund‐raising mechanism is an all‐pay auction augmented with an entry fee and reserve price.

Recently, economists have developed methods for structural estimation of auction models. Many researchers object to these methods because they find the strict rationality assumptions to be implausible. Using bid data from first‐price auction experiments, we estimate four alternative structural models: (1) risk‐neutral Bayes‐Nash, (2) risk‐averse Bayes‐Nash, (3) a model of learning, and (4) a quantal response model of bidding. For each model, we compare the estimated valuations and the valuations assigned to bidders in the experiments. We find that the risk aversion model is able to generate reasonable estimates of bidder valuations.

Abstract: In the 1990s Argentina embarked on one of the largest privatization campaigns in the world as part of a structural reform plan. The program included the privatization of local water companies covering approximately 30 percent of the country’s municipalities. Since clean water and sewage treatment are critical to control the spread of infectious and parasitic diseases; access expansions, quality improvements, and tariff changes associated to privatization may have affected health outcomes. Using the variation in ownership of water provision across time and space generated by the privatization process, we find that child mortality fell 5 to 7 percent in areas that privatized their water services overall; and that the effect was largest in the poorest areas. In fact, we estimate that child mortality fell by 24 percent in the poorest municipalities. These results suggest that the privatization of water services prevented approximately 375 deaths of young children per year. We check the robustness of these estimates using cause specific mortality. While privatization is associated with significant reductions in deaths from infectious