Ahmed Khwaja

Moral Hazard, Adverse Selection and Health Expenditures: A Semiparametric Analysis

Theoretical models predict asymmetric information in health insurance markets may generate inefficient outcomes due to adverse selection and moral hazard. However, previous empirical research has found it difficult to disentangle adverse selection from moral hazard in health care. We empirically study this question by using data from the Health and Retirement Study to estimate a structural model of the demand for health insurance and medical care. Using a two-step semi-parametric estimation strategy we find significant evidence of moral hazard, but not of adverse selection.

Habit Persistence and Teen Sex: Could Increased Access to Contraception Have Unintended Consequences for Teen Pregnancies?

We develop a dynamic discrete-choice model of teen sex and pregnancy that incorporates habit persistence. Habit persistence has two sources here. The first is a “fixed cost” of having sex, which relates to a moral or psychological barrier that has been crossed the first time one has sex. The second is a “transition cost,” whereby once a particular relationship has progressed to sex, it is difficult to move back. We estimate significant habit persistence in teen sex, implying that the long-run effects of contraception policy may be different from their short-run counterparts, especially if the failure rate of contraception is sufficiently large. Programs that increase access to contraception are found to decrease teen pregnancies in the short run but increase them in the long run.

Dynamic Entry with Cross Product Spillovers: An Application to the Generic Drug Industry

Experience in one product market can potentially improve firm performance in a related product market in the future. Thus, entry into a market is determined not just by profits in that market but also by its future impact on profitability in other markets. We formulate and estimate a dynamic model of entry decisions of firms in the presence of such spillovers using data on the generic drug industry. Spillovers imply that a firm’s unobserved “ability�? to profit in a product market not only changes stochastically but is also is endogenous to past entry decisions. Therefore, the model needs to accommodate unobserved state variables that are endogenous to firm actions and serially correlated. We address the methodological challenge of estimating such a model using a sequential importance sampling based technique. Our estimates show significant spillover effects of entry on future profits. On average, each entry reduces costs by 7% at the next entry opportunity. On average there are eight entry opportunities annually. The average cumulative benefit of a firm that enters all eight markets in a year is 51%. We conclude that spillovers are critical in the equilibrium evolution of the structure of the generic drug industry.

Do Smokers Value Their Health and Longevity Less

One reason why individuals consume harmful addictive goods is that the “full” price of such goods is low. Using data on adults specifically collected for this study, we examine the internal cost of one such good by estimating the value that smokers and nonsmokers place on loss of health and longevity from a major lung disease, chronic obstructive pulmonary disease (COPD). Differences in the nonpecuniary internal cost of getting COPD between current smokers and people who have never smoked range from

The Dynamic Spillovers of Entry: An Application to the Generic Drug Industry

80,000 to

Firm Expansion, Size Spillovers, and Market Dominance in Retail Chain Dynamics

260,000, implying that one reason people continue to smoke is that they face a lower full price of smoking. Our results suggest that although taxation and regulation of cigarettes may be justified for externality reasons, the principle of consumer sovereignty implies that the case is much weaker for interventions based on helping smokers internalize costs they impose on themselves.

The relationship between individual expectations and behaviors: Mortality expectations and smoking decisions

This paper examines whether experience from entry in one market can potentially enhance profitability at a future market opportunity for a related product. We formulate and estimate a dynamic game of entry in which forward-looking firms make decisions not just based on present benefits of past entry but also anticipating potential future benefits of current entry. Dynamic spillovers of entry are incorporated through a firm-specific unobservable to the researcher cost that depends on past entry decisions. The unobserved costs may also be serially persistent. Thus, the model allows for firm-specific unobserved heterogeneity that evolves based on firm actions. The challenge of estimating a dynamic game with serially correlated unobserved state variables subject to endogenous feedback is overcome by embedding a particle filter-based technique in a nested fixed-point algorithm. Using an application to a stylized model of entry in the generic pharmaceutical industry, we underscore the motivation for the model specification and the methodology developed. Our estimates imply positive spillover effects of entry. Moreover, these spillovers suggest heterogeneity not just across firms but also within firms over time based on their history of entry decisions. Our results illustrate that entry may potentially provide firms with additional strategic advantage in later markets and that entry spillovers may be an important factor to consider in the equilibrium evolution of the generic drug industry. The web appendix is available at https://doi.org/10.1287/mnsc.2016.2648 . This paper was accepted by J. Miguel Villas-Boas, marketing.

Evidence on preferences and subjective beliefs of risk takers: The case of smokers

We develop and estimate a dynamic game of strategic firm expansion and contraction decisions to study the role of firm size in future profitability and market dominance. Modeling firm size is important because retail chain dynamics are more richly driven by expansion and contraction than de novo entry or permanent exit. Additionally, anticipated size spillovers may influence the strategies of forward-looking firms, making it difficult to analyze the effects of size without explicitly accounting for these in the expectations and, hence, decisions of firms. Expansion may also be profitable for some firms while detrimental for others. Thus, we explicitly model and allow for heterogeneity in the dynamic link between firm size and profits as well as potential for persistent brand effects through firm-specific unobservable factors. As a methodological contribution, we surmount the hurdle of estimating the model by extending a two-step procedure that circumvents solving the game. The first stage combines semipar...