We use new PSID data on consumption and health, along with information on annual sick time, to estimate a structural labor supply model that incorporates a health capital stock with the traditional human capital learning-by-doing model. The estimates show strong evidence of learning by doing as well as strong persistence in health. However, the estimates reveal that time and money seem to have little effect on health consistent with 'flat of the curve' medicine. We find strong evidence that consumption and leisure are direct substitutes in preferences, and consumption and leisure are each utility complements with good health.

The newsworthiness of an event is partly determined by how unusual it is and this paper investigates the business cycle implications of this fact. Signals that are more likely to be observed after unusual events may increase both uncertainty and disagreement among agents. In a simple business cycle model, such signals can explain why we observe (i) occasional large changes in macroeconomic aggregate variables without a correspondingly large change in underlying fundamentals, (ii) persistent periods of high macroeconomic volatility and, (iii) a positive correlation between absolute changes in macrovariables and the cross-sectional dispersion of survey expectations.

We provide a simple quantitative general equilibrium model of occupational choice with credit market frictions to analyze the aggregate and distributional effects of asset transfer programs. Asset transfer programs have a positive but transient effect on aggregate productivity, and a negative impact on the aggregate capital stock. On net they have a negative but small effect on per capita income. The effects are very heterogeneous across treated individuals. We compare the results in our model to those from recent randomized control trials and historical natural experiments.

We build a theoretical model of multi-product firms that highlights how competition across market destinations affects both a firm’s exported product range and product mix. We show how tougher competition in an export market induces a firm to skew its export sales toward its best performing products. We find very strong confirmation of this competitive effect for French exporters across export market destinations. Theoretically, this within-firm change in product mix driven by the trading environment has important repercussions on firm productivity. A calibrated fit to our theoretical model reveals that these productivity effects are potentially quite large.

Mortality gradients by education and income have been rising in the United States and elsewhere. However, their impact on Social Security progressivity has received relatively little attention, and the impact on Medicare has received effectively none. This paper uses the Future Elderly Model to estimate the effects of increased mortality gaps on the progressivity of Social Security and Medicare for those born between 1928 and 1990. It finds significant reductions in progressivity of both programs if current mortality trends persist and noticeable effects on total program costs. The effects are large enough to warrant more attention from both policy-makers and researchers.

We define the empirical content of an economic theory as the least restrictive observationally equivalent theory. We show that the empirical content of a theory is captured by a certain kind of axiomatization, with axioms that are universal negations of conjunctions of atomic formulae.

We develop a model of households with multiple needs (smoothing shocks, financing investment) and constraints (limited credit, self-control issues) in order to examine the nature of household's financing constraints in a developing country, and the impact of relaxing them. We show that increased access to credit has very different implications for the aggregate model economy depending on its form: asset-financed or cash. We then illustrate how a short-term increase in access to loans leads to very distinct behavior in the short run. The relevance of the model can be evaluated using a field experiment, which we are currently implementing in Uganda.

We provide novel insights on the decentralization of optimal outcomes under monopolistic competition with nonseparable utility, variable demand elasticity, and endogenous firm heterogeneity. Relative to the unconstrained optimum, equilibrium firm selection is too weak, average firm size is too small, low-cost firms are too small, and high-cost firms are too large. The unconstrained optimum can be decentralized through differentiated production subsidies to producers financed through lump-sum taxes on entrants and consumers. When differentiated subsidies and transfers from entrants are not viable, the constrained optimum can be decentralized through a common production subsidy financed by a lump-sum tax on consumers.

The mobile applications (apps) industry has exhibited rapid entry and growth in the midst of a recession. Using unique data from the iPhone application ecosystem, we examine how the development of 'killer apps' (apps appearing in the top grossing rank) varies by market and app characteristics. We find that previous app experience and no updating increase the likelihood of becoming a killer game app, while more updates increase the likelihood of becoming a non-game killer app. Development opportunities, level of competition, and demand preferences are possible drivers of the opposing innovation process results in game and non-game markets.