Knowledge that Transforms

We construct an infinite horizon model of harmful addiction. Consumption is compulsive if it differs from what the individual would have chosen had commitment been available. A good is addictive if its consumption leads to more compulsive consumption of the same good. We analyse the welfare implications of drug policies and find that taxes on drugs decrease welfare while prohibitive policies may increase welfare. We also analyse the agent's demand for voluntary commitment (“rehab”). For appropriate parameters, the model predicts a cycle of addiction where the agent periodically checks into rehab. Between these visits his drug consumption increases each period.

During financial disruptions, marketmakers provide liquidity by absorbing external selling pressure. They buy when the pressure is large, accumulate inventories, and sell when the pressure alleviates. This paper studies optimal dynamic liquidity provision in a theoretical market setting with large and temporary selling pressure, and orderexecution delays. I show that competitive marketmakers offer the socially optimal amount of liquidity, provided they have access to sufficient capital. If raising capital is costly, this suggests a policy role for lenient central-bank lending during financial disruptions.

Does capital-embodied technological change play an important role in shaping labour-market outcomes? To address this question, we develop a model with vintage capital and search-matching frictions where irreversible investment in new vintages of capital creates heterogeneity in productivity among firms, matched as well as vacant. We demonstrate that capital-embodied technological change reduces labour demand and raises equilibrium unemployment and unemployment durations. In addition, the presence of labour-market regulations (unemployment benefits, payroll taxes, and firing costs) exacerbates these effects. Thus, the model is qualitatively consistent with some key features of the European labour-market experience relative to that of the U.S.: it features a sharper rise in unemployment and a sharper fall in the vacancy rate and the labour share. A calibrated version of our model suggests that this technology—policy interaction could explain a sizeable fraction of the observed differences between the U.S. and Europe. Copyright 2007, Wiley-Blackwell.

We develop a transferable utility model of the household in which the marriage market is characterized by (negative or positive) assortative matching, and spousal allocations are determined by premarital investments. We demonstrate that all sharing rules along the assortative order support efficient outcomes both in terms of premarital investments and intra-household allocations. The efficiency of premarital choices and household allocations then enables us to show that, for each couple, the marriage market generates a unique and maritally sustainable sharing rule that is a function of the distribution of premarital endowments and the sex ratios in the market. According to our results, transfers among spouses occur on two margins: premarital investments and intra-marital spousal allocations. Asymmetries in the sex ratios in the marriage markets produce gender differences in premarital investments and consumption that are larger for individuals with small premarital endowments than those with larger endowments. A corollary of these findings is that, when men are in short supply in the marriage markets, women can invest more than men even when the returns to investment are lower or the costs are higher for women.

Towards developing a theory of systematic biases about strategies, I analyze strategic implications of a particular bias: wishful thinking about the strategies. Considering canonical state spaces for strategic uncertainty, I identify a player as a wishful thinker at a state if she hopes to enjoy the highest payoff that is consistent with her information about the others’ strategies at that state. I develop a straightforward elimination process that characterizes the strategy profiles that are consistent with wishful thinking, mutual knowledge of wishful thinking, and so on. Every pure-strategy Nash equilibrium is consistent with common knowledge of wishful thinking. For generic two-person games, I further show that the pure Nash equilibrium strategies are the only strategies that are consistent with common knowledge of wishful thinking, providing an unusual epistemic characterization for equilibrium strategies. I also investigate the strategic implications of rationality and ex-post optimism, the situation in which a player’s expected payoff weakly exceeds her actual payoff. I show that these strategic implications are generically identical to those of wishful thinking whenever each player’s payoff is monotone in others ’ strategies.

Institutions—quality of contract enforcement, property rights, shareholder protection, and the like—have received a great deal of attention in recent years. Yet trade theory has not considered the implications of institutional differences, beyond treating them simply as different technologies or taxes. The purpose of this paper is twofold. First, we propose a simple model of international trade in which institutional differences are modelled within the framework of incomplete contracts. We show that doing so reverses many of the conclusions obtained by equating institutions with productivity. Institutional differences as a source of comparative advantage imply, among other things, that the less developed country may not gain from trade and factor prices may actually diverge as a result of trade. Second, we test empirically whether institutions act as a source of trade, using data on U.S. imports disaggregated by country and industry. The empirical results provide evidence of “institutional content of trade”: institutional differences are an important determinant of trade flows.

This paper considers the role of foreign investors in developed country equity markets. It presents a quantitative model of trading that is built around two new assumptions about investor sophistication: (i) both the foreign and domestic populations contain investors with superior information sets; and (ii) these knowledgeable investors have access to both public equity markets and private investment opportunities. The model delivers a unified explanation for three stylized facts about U.S. investors' international equity trades: (i) trading by U.S. investors occurs in waves of simultaneous buying and selling; (ii) U.S. investors build and unwind foreign equity positions gradually; and (iii) U.S. investors increase their market share in a country when stock prices there have recently been rising. The results suggest that heterogeneity within the foreign investor population is much more important than heterogeneity of investors across countries. Copyright 2007, Wiley-Blackwell.

We report experimental results from long sequences of decisions in environments that are theoretically prone to severe information cascades. Observed behaviour is much different—information cascades are ephemeral. We study the implications of a theoretical model based on quantal response equilibrium, in which the observed cascade formation/collapse/formation cycles arise as equilibrium phenomena. Consecutive cascades may reverse states, and usually such a reversal is self-correcting: the cascade switches to the correct state. These implications are supported by the data. We extend the model to allow for base rate neglect and find strong evidence for overweighting of private information. The estimated belief trajectories indicate fast and efficient learning dynamics.

Robert Wilson criticizes applied game theory's reliance on common-knowledge assumptions. In reaction to Wilson's critique, the recent literature of mechanism design has adopted the goal of finding detail-free mechanisms in order to eliminate this reliance. In practice this has meant restricting attention to simple mechanisms such as dominant-strategy mechanisms. However, there has been little theoretical foundation for this approach. In particular it is not clear the search for an optimal mechanism that does not rely on common-knowledge assumption would lead to simpler mechanisms rather than more complicated ones. This paper tries to fill the void. In the context of an expected revenue maximizing auctioneer, we investigate some foundations for using simple, dominant-strategy auctions.

The paper estimates and examines the empirical plausibility of asset pricing models that attempt to explain features of financial markets such as the size of the equity premium and the volatility of the stock market. In one model, the long-run risks (LRR) model of Bansal and Yaron, low-frequency movements, and time-varying uncertainty in aggregate consumption growth are the key channels for understanding asset prices. In another, as typified by Campbell and Cochrane, habit formation, which generates time-varying risk aversion and consequently time variation in risk premia, is the key channel. These models are fitted to data using simulation estimators. Both models are found to fit the data equally well at conventional significance levels, and they can track quite closely a new measure of realized annual volatility. Further, scrutiny using a rich array of diagnostics suggests that the LRR model is preferred.