Knowledge that Transforms

We examine an oligopoly model where some consumers engage in costly non-sequential search to discover prices. There are three distinct price-dispersed equilibria characterized by low, moderate and high search intensity. The effects of an increase in the number of firms on search behaviour, expected prices, price dispersion and welfare are sensitive (i) to the equilibrium consumers' search intensity, and (ii) to the status quo number of firms. For instance, when consumers search with low intensity, an increase in the number of firms reduces search, does not affect expected price, leads to greater price dispersion and reduces welfare. In contrast, when consumers search with high intensity, increased competition results in more search and lower prices when the number of competitors in the market is low to begin with, but in less search and higher prices when the number of competitors is large. Duopoly yields identical expected price and price dispersion but higher welfare than an infinite number of firms.

When does an individual's expected wealth accumulation profile increase as earnings risk increases? This paper answers this question for multi-period models where earnings shocks are independent over time. Sufficient conditions are stated in terms of properties of a decision rule for savings and, alternatively, in terms of properties of preferences. Copyright 2004, Wiley-Blackwell.

Models of labour market equilibrium where forward-looking decisions maximize both profits and labour income on a risk-neutral basis offer valuable insights into the effects of employment protection legislation. Since risk-neutral behaviour in the labour market presumes perfect insurance, however, job security provisions plays no useful role in such models. This paper studies a stylized model of dynamic labour market interactions where labour reallocation costs are partly financed by uninsured workers' consumption flows. In the resulting second-best equilibrium, provisions that shift labour reallocation costs to risk-neutral employers can increase productive efficiency if their administrative dead-weight costs are not too large, and increase workers' welfare as long as employers' firing costs at least partly finance workers' mobility. Copyright 2004, Wiley-Blackwell.

This paper identifies a source of gradualism in bargaining and contribution games. In the bargaining games we examine, each party can opt out at any time, and the outside option outcome is assumed to depend on the offers made in the negotiation phase. Specifically, we assume that (1) making a concession in the negotiation phase increases the other party's outside option pay-off and (2) the outside option outcome induces an efficiency loss as compared with a negotiated agreement. The main finding is that the mere presence of such history-dependent outside options forces equilibrium concessions in the negotiation phase to be gradual, and the degree of gradualism is characterized. The model also applies to contribution games in which the outside option may be interpreted as the option to implement a partial project using the total contributions made so far.

This paper provides a model of boom-bust episodes in middle-income countries. It is based on sectoral differences in corporate finance: the nontradables sector is special in that it faces a contract enforceability problem and enjoys bailout guarantees. As a result, currency mismatch and borrowing constraints arise endogenously in that sector. This sectoral asymmetry allows the model to replicate the main features of observed boom-bust episodes. In particular, episodes begin with a lending boom and a real appreciation, peak in a self-fulfilling crisis during which a real depreciation coincides with widespread bankruptcies, and end in a recession and credit crunch. The nontradables sector accounts for most of the volatility in output and credit. Copyright 2004, Wiley-Blackwell.

We develop a general model of lending in the presence of endogenous borrowing constraints. Borrowing constraints arise because borrowers face limited liability and debt repayment cannot be perfectly enforced. In the model, the dynamics of debt are closely linked with the dynamics of borrowing constraints. In fact, borrowing constraints must satisfy a dynamic consistency requirement: the value of outstanding debt restricts current access to short-term capital, but is itself determined by future access to credit. This dynamic consistency is not guaranteed in models of exogenous borrowing constraints, where the ability to raise short-term capital is limited by some prespecified function of debt. We characterize the optimal default-free contract—which minimizes borrowing constraints at all histories—and derive implications for firm growth, survival, leverage and debt maturity. The model is qualitatively consistent with stylized facts on the growth and survival of firms. Comparative statics with respect to technology and default constraints are derived.

I analyse social interactions that stem from the successive endeavours of new cohorts of heterogeneous decision makers to learn from the experiences of past cohorts. A dynamic process of information accumulation and decision making occurs as the members of each cohort observe the experiences of earlier ones, and then make choices that yield experiences observable by future cohorts. Decision makers face the "selection problem" as they seek to learn from observation of past actions and outcomes, while not observing the counterfactual outcomes that would have occurred had other actions been chosen. Assuming that all cohorts face the same outcome distributions, I show that social learning is a process of sequential reduction in ambiguity. The specific nature of this process, and its terminal state, depend critically on how decision makers make choices under ambiguity. I use the problem of learning about innovations to illustrate. Copyright The Review of Economic Studies Limited, 2004.

We consider an infinitely repeated Bertrand game, in which prices are publicly observed and each firm receives a privately observed, i.i.d. cost shock in each period. We focus on symmetric perfect public equilibria, wherein any “punishments” are borne equally by all firms. We identify a tradeoff that is associated with collusive pricing schemes in which the price to be charged by each firm is strictly increasing in its cost level: such “fully sorting” schemes offer efficiency benefits, as they ensure that the lowest-cost firm makes the current sale, but they also imply an informational cost (distorted pricing and/or equilibrium-path price wars), since a higher-cost firm must be deterred from mimicking a lower-cost firm by charging a lower price. A rigid-pricing scheme, where a firm's collusive price is independent of its current cost position, sacrifices efficiency benefits but also diminishes the informational cost. For a wide range of settings, the optimal symmetric collusive scheme requires (i) the absence of equilibrium-path price wars and (ii) a rigid price. If firms are sufficiently impatient, however, the rigid-pricing scheme cannot be enforced, and the collusive price of lower-cost firms may be distorted downward in order to diminish the incentive to cheat. When the model is modified to include i.i.d. public demand shocks, the downward pricing distortion that accompanies a firm's lower-cost realization may occur only when current demand is high.

This paper presents a model of dynamic competition between two firms that repeatedly engage in an innovative activity. The state of competition—measured by the difference between the number of innovations introduced by the firms—evolves stochastically according to their effort level. The structure of Markov perfect equilibria is identified. It is generally not true that competition is fiercest when firms are closest. Rather, firms invest under two distinct circumstances: while sufficiently ahead, to outstrip their rival and secure a durable leadership; while behind, to regain leadership and prevent the situation from worsening to the point where their rival outstrips them.

This paper describes a search model with a continuum of worker and job types, free entry and transferable utility. We apply a second-order Taylor expansion to characterize the equilibrium, derive the "cost of search" and show that it is decreasing in the substitutability of worker types. This cost of search is then decomposed into three components: unemployment, vacancy costs and mismatch. Our contact technology rules out congestion effects between different worker types and therefore exhibits increasing returns to scale. One third of those increasing returns in contacts are shown to be absorbed by firms and workers being more choosy. The resulting equilibrium is not efficient. Unemployment benefits can reduce the loss by serving as a search subsidy. Numerical simulations of the model show that our Taylor expansions are quite accurate. © 2004 The Review of Economics Studies Limited.