A large literature describes relationships between month of birth, birth weight, and gestation. These relationships are hypothesized to reflect the causal impact of seasonal environmental factors. However, recent work casts doubt on this interpretation by showing that mothers with lower socioeconomic status are more likely to give birth in months that are associated with poorer birth outcomes. Seasonality in the numbers of conceptions in different months can also induce a mechanical correlation between preterm birth and month of birth. This paper analyzes the seasonality of health at birth using a large sample of 647,050 groups of US siblings representing 1,435,213 children. By following the same mother over time, we eliminate differences in fixed maternal characteristics as an explanation for seasonal differences in health at birth. We find a sharp trough in gestation length among babies conceived in May, which corresponds to an increase in prematurity of more than 10%. Birth weight conditional on gestation length, however, is found to be strongly hump-shaped over the year, with 8–9 additional g for summer conceptions. We examine several potential mechanisms for explaining seasonality in birth outcomes that have generally been dismissed in the literature on seasonality in rich countries, notably disease prevalence and nutrition. The May trough in gestation length coincides with a higher influenza prevalence in January and February, when these babies are nearing full term, whereas the hump shape in birth weight is associated with a similar pattern in pregnancy weight gain.
Mortality is a crucial dimension of wellbeing and inequality in a population, and mortality trends have been at the core of public debates in many Western countries. In this paper, we provide the first analysis of mortality inequality in Canada and compare its development to trends in the U.S. We find strong reductions in mortality rates across both genders and at all ages, with the exception of middle ages which only experienced moderate improvements. Inequality in mortality, measured across Canadian Census Divisions, decreased for infants and small children, while it increased slightly at higher ages. In comparison to the U.S., mortality levels in Canada improved at a similar rate despite lower initial levels. Inequality at younger ges, however, fell more strongly in the U.S., implying converging mortality gradients between the two countries.
Many literatures investigate the causal impact of income on economic outcomes, for example in the context of intergenerational transmission or well-being and health. Some studies have proposed to use employer wage differentials and in particular industry affiliation as an instrument for income. We demonstrate that industry affiliation is correlated with fixed individual characteristics, specifically parents' education and own height, conditional on the covariates typically controlled for in these studies. These results suggest that there is selection into industries based on unobservables. As a result the exclusion restriction in many IV studies of this type is likely violated.
Corruption is a widespread phenomenon. Nevertheless, causal evidence on the effects of corruption is still lacking. In this paper, we assess whether and how corruption affects cooperation using a public good game experiment. Overall, contributions to the public good are reduced by 30% when participants have the possibility to bribe the punishment authority. Two concurrent channels lead to lower levels of cooperation. First, the punishment of low contributors decreases both at the intensive and the extensive margin. Second, bribery discourages initially high contributors, who gradually decrease their contributions down to the level of initially low contributors.
This paper studies Pareto-optimal risk-sharing arrangements in a private information economy with aggregate uncertainty and ex ante heterogeneous agents. I show how to implement Pareto optima as equilibria when agents can trade claims to consumption contingent on aggregate shocks in financial markets. The first result is that if aggregate and idiosyncratic shocks are independent, the implementation of optimal allocations does not require any interventions in financial markets. This result can be extended to dynamic settings in the sense that, in this case, only savings need to be distorted, but not trades in financial markets. Second, I characterize optimal trading distortions in financial markets when aggregate and idiosyncratic shocks are not independent. In this case, optimal asset taxes must be higher for those securities that pay out in aggregate states in which consumption is more volatile. For instance, this can provide an efficiency justification for the frequently observed differential tax treatment of different asset classes, such as debt and equity claims.
Health economists have studied the determinants of the expected value of health status as a function of medical and nonmedical inputs, often finding small marginal effects of the former. This paper argues that both types of input have an additional benefit, viz. a reduced variability of health status. Using OECD health data for 24 countries between 1960 and 2004, medical and nonmedical inputs are found to reduce the variability of life expectancy. While the evidence supports the "flat-of-the-curve medicine" hypothesis with respect to the expected value of life expectancy and its variability, healthcare expenditure is comparatively effective in reducing variability.
Public attention has focused on how the launch of the national health exchanges could impact the types of risks who initially enroll and thereby affect future premiums and enrollment. We introduce simple dynamics into a standard model of insurance under adverse selection to show that such "initial conditions" can indeed matter. When firms are price-takers, the market can converge to a Pareto-inferior "bad" equilibrium if there are at least three equilibria, which we suggest has empirical support. Strategic pricing eliminates Pareto dominated equilibria but requires common knowledge of preference and risk distributions. Changing the fine on non-participants from a fixed amount to a fraction of equilibrium prices increases the range of initial conditions consistent with reaching the "good" equilibrium while reducing the "badness" of the bad equilibrium -- all without increasing the fine value in the good equilibrium. Allowing insurers to quickly change prices can encourage them to experiment with strategic pricing if market fundamentals are not perfectly known, increasing the chance of reaching the good equilibrium independently from initial conditions.
We develop a unifying framework for optimal income taxation in multi-sector economies with general patterns of externalities. Agents in this model are characterized by an N-dimensional skill vector corresponding to intrinsic abilities in N potentially externality-causing activities. The private return to each activity depends on individual skill and an aggregate activity-specific return, which is a fully general function of the economy-wide distribution of activity-specific efforts. We show that the N-dimensional heterogeneity can be collapsed to a one-dimensional, endogenous statistic sufficient for screening. The optimal tax schedule features a multiplicative income-specific correction to an otherwise standard tax formula. Because externalities change the relative returns to different activities, corrective taxes induce changes in the across-activity allocation of effort. These relative return effects cause the optimal correction to diverge, in general, from the Pigouvian tax that would align private and social returns. We characterize this divergence and its implications for the shape of the tax schedule both generally and in a number of applications, including externality-free economies, increasing and decreasing returns to scale, zero-sum activities such as bargaining or rent extraction, and positive or negative spillovers.
We show that the Diamond and Mirrlees (1971) linear tax model contains the Mirrlees (1971) nonlinear tax model as a special case. In this sense, the Mirrlees model is an application of Diamond-Mirrlees. We also derive the optimal tax formula in Mirrlees from the Diamond-Mirrlees formula. In the Mirrlees model, the relevant compensated cross-price elasticities are zero, providing a situation where an inverse elasticity rule holds. We provide four extensions that illustrate the power and ease of our approach, based on Diamond-Mirrlees, to study nonlinear taxation. First, we consider annual taxation in a lifecycle context. Second, we include human capital investments. Third, we incorporate more general forms of heterogeneity into the basic Mirrlees model. Fourth, we consider an extensive margin labor force participation decision, alongside the intensive margin choice. In all these cases, the relevant optimality condition is easily obtained as an application of the general Diamond-Mirrlees tax formula.
In many countries, taxes on businesses are less progressive than labor income taxes. This paper provides a justification for this pattern based on adverse selection that entrepreneurs face in credit markets. Individuals choose between becoming entrepreneurs or workers and differ in their skill in both of these occupations. I find that endogenous cross-subsidization in the credit market equilibrium results in excessive (insufficient) entry of low-skilled (high-skilled) agents into entrepreneurship. This gives rise to a corrective role for differential taxation of entrepreneurial profits and labor income. In particular, a profit tax that is regressive relative to taxes on labor income restores the efficient occupational choice.
