Knowledge that Transforms

This paper shows that in a general equilibrium model with an infinite horizon in which production may exhibit increasing returns to scale or non-convexities, marginal cost pricing equilibria exist and are essential, that is, stable with respect to small perturbations of the economy. As in many important models of market imperfections, marginal cost pricing equilibria need not be Pareto optimal in the presence of non-convexities, so the systematic approaches to equilibrium analysis in infinite-dimensional commodity spaces, which rely crucially on the First Welfare Theorem, cannot be used. Instead, this paper introduces Leray-Schauder degree theory, the extension of degree theory to Banach and locally convex spaces, as the natural methodology for showing that equilibria exist and for analyzing qualitative features of equilibria such as local uniqueness or essentiality.

This paper explores two models of an economy in which contracts are exchanged. In the first model contracts are exchanged on a competitive market in which traders expectations concerning conditions that prevail within specific markets adjust until markets "clear" In the second model contract designers compete directly against one another by offering alternate contracts. It is shown that Walrasian allocations correspond with the equilibrium allocations in the model with direct competition when the number of traders is made large. Furthermore, the expectational assumptions that drive the Walrasian analysis coincide with off the equilibrium path conjectures in the problem with direct competition.

This paper considers whether it is possible to devise a nonexperimental procedure for evaluating a prototypical job training programme. Using rich nonexperimental data, we examine the performance of a two-stage evaluation methodology that (a) estimates the probability that a person participates in a programme and (b) uses the estimated probability in extensions of the classical method of matching. We decompose the conventional measure of programme evaluation bias into several components and find that bias due to selection on unobservables, commonly called selection bias in econometrics, is empirically less important than other components, although it is still a sizeable fraction of the estimated programme impact. Matching methods applied to comparison groups located in the same labour markets as participants and administered the same questionnaire eliminate much of the bias as conventionally measured, but the remaining bias is a considerable fraction of experimentally-determined programme impact estimates. We test and reject the identifying assumptions that justify the classical method of matching. We present a nonparametric conditional difference-in-differences extension of the method of matching that is consistent with the classical index-sufficient sample selection model and is not rejected by our tests of identifying assumptions. This estimator is effective in eliminating bias, especially when it is due to temporally-invariant omitted variables.

This paper deals with the evaluation of some public employment policies set up in France during the 1980's to improve the labour market prospects of unskilled young workers. The evaluation implemented in this paper is restricted to the impact of such public measures on durations and outcomes of subsequent spells of unemployment and employment. The econometric study is conducted with non-experimental longitudinal microdata recording individual labour market histories. A particular attention is paid to the differential effects of various types of measures, according to the educational level of recipients. Programmes involving a higher level of on-the-job training, such as alternating work/training programmes in private firms, are principally beneficial to the less educated young workers. In contrast, for more educated young workers, “work fare” programmes in the public sector decrease the intensity of transition from the subsequent unemployment spell to regular jobs; for that subgroup, “work fare” programmes may act as a signal of low employment performance.

The authors address two questions using experimental data on disadvantaged women. First, what is the impact of being offered Job Training Partnership Act classroom training on the duration of unemployment and employment? Second, what is the effect of actually participating in this training on the length of such spells? Belonging to the treatment group shortens unemployment spells but has no effect on employment spells. Actually participating in training has a larger positive effect on the exit rate from unemployment than the effect of simply being a member of the treatment group. Ignoring the endogeneity of actual training in estimation substantially underestimates its effect. Copyright 1997 by The Review of Economic Studies Limited.

This paper investigates foreign exchange trading, a phenomenon that typically accompanies international trade. A search-theoretic general equilibrium approach is adopted to study a two-country, two-currency model. For some parameter values of the model, there exist some pure-strategy equilibria in which commodity-currency trade is conducted primarily through local currency and in which there is active currency-currency exchange. The coexistence of valued foreign currency and its local non-acceptability conforms largely with the country-specific cash-in-advance constraint that is often assumed exogenously in international finance literature.

In Imbens and Ingrist (1994), Angrist, Imbens and Rubin (1996) and Imbens and Rubin (1997), assumptions have been outlined under which instrumental variables estimands can be given a causal interpretation as a local average treatment effect without requiring functional form or constant treatment effect assumptions. We extend these results by showing that under these assumptions one can estimate more from the data than the average causal effect for the subpopulation of compliers; one can, in principle, estimate the entire marginal distribution of the outcome under different treatments for this subpopulation. These distributions might be useful for a policy maker who wishes to take into account not only differences in average of earnings when contemplating the merits of one job training programme vs. another. We also show that the standard instrumental variables estimator implicitly estimates these underlying outcome distributions without imposing the required nonnegativity on these implicit density estimates, and that imposing non-negativity can substantially alter the estimates of the local average treatment effect. We illustrate these points by presenting an analysis of the returns to a high school education using quarter of birth as an instrument. We show that the standard instrumental variables estimates implicitly estimate the outcome distributions to be negative over a substantial range, and that the estimates of the local average treatment effect change considerably when we impose nonnegativity in any of a variety of ways.

This paper explores the link between financial market incompleteness and human capital accumulation. We examine how child school attendance responds to seasonal fluctuations in the income of agrarian households using panel data from rural India. To pinpoint market imperfections, we study responses to aggregate and idiosyncratic, as well as to anticipated and unanticipated, income shocks. Our main finding is that seasonal fluctuations in school attendance are a form of self-insurance, but one which does not result in a substantial loss of human capital on average.

In this paper, we consider what can be learned about causal effects when one uses a contaminated instrumental variable. In particular, we consider what inferences can be made about the causal effect of teenage childbearing on a teen mother's subsequent outcomes when we use the natural experiment of miscarriages to form an instrumental variable for teen births. Miscarriages might not meet all of the conditions required for an instrumental variable to identify such causal effects for all of the observations in our sample. However, it is an appropriate instrumental variable for some women, namely those pregnant women who experience a random miscarriage. Although information from typical data sources does not allow one to identify these women, we show that one can adapt results from Horowitz and Manski (1995) on identification with data from contaminated samples to construct informative bounds on the causal effect of teenage childbearing. We use these bounds to re-examine the effects of early chilbearing on the teen mother's subsequent educational and labour market attainment as considered in Hotz, McElroy and Sanders (1995a, 1995b). Consistent with their study, these bounds indicate that women who have births as teens have higher labour market earnings and hours worked compared to what they would have attained if their childbearing had been delayed.

This paper analyses competition among financial intermediaries in a set-up where financial intermediaries economize on duplicated monitoring (Diamond (1984)). We analyse two different games in which both direct trade and indirect trade are available. We show that in general equilibrium outcomes are inefficient, so that Diamond's efficiency result is fragile. Intermediation may increase rather than decrease transaction costs. Disintermediation may also be an equilibrium. We discuss the role played by the nonconvexities of banks' technology and that played by competition for deposits and loans.