Knowledge that Transforms

A medical treatment is said to have placebo effects if patients who are optimistic about the treatment respond better to the treatment. This paper proposes a simple test for placebo effects. Instead of comparing the treatment and control arms of a single trial, one should compare the treatment arms of two trials with different probabilities of assignment to treatment. If there are placebo effects, patients in the higher‐probability trial will experience better outcomes simply because they believe that there is a greater chance of receiving treatment. This paper finds evidence of placebo effects in trials of antiulcer and cholesterol‐lowering drugs.

We develop a framework for valuing improvements in health and apply it to past and prospective reductions in mortality in the United States. We calculate social values of (i) increased longevity over the twentieth century, (ii) progress against various diseases after 1970, and (iii) potential future progress against major diseases. Cumulative gains in life expectancy after 1900 were worth over $1.2 million to the representative American in 2000, whereas post-1970 gains added about $3.2 trillion per year to national wealth, equal to about half of GDP. Potential gains from future health improvements are also large; for example, a 1 percent reduction in cancer mortality would be worth $500 billion.

This paper proposes and estimates a static transferable utility model of the marriage market. The model generates a nonparametric marriage matching function with spillover effects. It rationalizes the standard interpretation of marriage rate regressions and points out its limitations. The model was used to estimate U.S. marital behavior in 1971/72 and 1981/82. The marriage matching function estimates show that the gains to marriage for young adults fell substantially over the decade. Unlike contradictory marriage rate regression results, the marriage matching function estimates showed that the legalization of abortion had a significant quantitative impact on the fall in the gains to marriage for young men and women.

We develop a dynamic model of experience goods pricing with independent private valuations. We show that the optimal paths of sales and prices can be described in terms of a simple dichotomy. In a mass market, prices are declining over time. In a niche market, the optimal prices are initially low followed by higher prices that extract surplus from the buyers with a high willingness to pay. We consider extensions of the model to integrate elements of social rather than private learning and turnover among buyers.

Do Walrasian markets function orderly in the presence of adverse selection? In particular, is their outcome efficient when exclusive contracts are enforceable? This paper addresses these questions in the context of a Rothschild‐Stiglitz insurance economy. We identify an externality associated with the presence of adverse selection as a special form of consumption externality. Consequently, we show that competitive equilibria always exist but are not typically incentive efficient. However, as markets for pollution rights can internalize environmental externalities, markets for consumption rights can be designed to internalize the consumption externality due to adverse selection. With such markets competitive equilibria exist and incentive‐constrained versions of the first and second welfare theorems hold.

We solve each household’s optimal saving decisions using a life cycle model that incorporates uncertain lifetimes, uninsurable earnings and medical expenses, progressive taxation, government transfers, and pension and social security benefits. With optimal decision rules, we compare, household by household, wealth predictions from the life cycle model using a nationally representative sample. We find, making use of household‐specific earnings histories, that the model accounts for more than 80 percent of the 1992 cross‐sectional variation in wealth. Fewer than 20 percent of households have less wealth than their optimal targets, and the wealth deficit of those who are undersaving is generally small.

We compare the performance of organizational forms (M‐form and U‐form) in experimenting with uncertain projects. In our framework, organizational forms affect the information structure of an organization and thus the way to coordinate changes. Compared to the U‐form, the M‐form organization achieves better coordination in “attribute matching” but suffers from coordination in “attribute compatibility” and less gains in specialization. The distinctive advantage of the M‐form is its flexibility in choosing between small‐scale and full‐scale experimentation.

A Bayesian consumer who is uncertain about the quality of an information source will infer that the source is of higher quality when its reports conform to the consumer's prior expectations. We use this fact to build a model of media bias in which firms slant their reports toward the prior beliefs of their customers in order to build a reputation for quality. Bias emerges in our model even though it can make all market participants worse off. The model predicts that bias will be less severe when consumers receive independent evidence on the true state of the world and that competition between independently owned news outlets can reduce bias. We present a variety of empirical evidence consistent with these predictions.

The role of the market in mitigating and mediating various forms of behavior is perhaps the central issue facing behavioral economics today. This study designs a field experiment that is explicitly linked to a controlled laboratory experiment to examine whether, and to what extent, social preferences influence outcomes in actual market transactions. While agents drawn from a well‐functioning marketplace behave in accord with social preference models in tightly controlled laboratory experiments, when they are observed in their naturally occurring settings, their behavior approaches what is predicted by self‐interest theory. In the limit, much of the observed behavior in the marketplace that is consistent with social preferences is due to reputational concerns: suppliers who expect to have future interactions with buyers provide higher product quality only when the buyer can verify quality via a third‐party certifier. The data also speak to theories of how reputation effects enhance market performance. In particular, reputation and the monitoring of quality are found to be complements, and findings suggest that the private market can solve the lemons problem through third‐party verification.

We incorporate multiagent, principal‐agent theory into general equilibrium analysis. The traded commodities are multiagent contracts that include a description of the individual’s job, effort level, and state‐contingent consumption. These contracts are club goods. The competitive equilibrium and the Pareto program are formulated. The contracts are identified with firms, so the market determines which firms exist and who is assigned to which firm in what capacity. An example is provided in which the internal organization of firms and the distribution of firm classes vary with the aggregate capital endowment and its distribution across agents. A simplex‐based algorithm for solving the Pareto program is developed.