This paper summarizes the contributions of microeconometrics to economic knowledge. Four main themes are developed. (1) Microeconometricians developed new tools to respond to econometric problems raised by the analysis of the new sources of micro data produced after the Second World War. (2) Microeconometrics improved on aggregate time-series methods by building models that linked economic models for individuals to data on individual behavior. (3) An important empirical regularity detected by the field is the diversity and heterogeneity of behavior. This heterogeneity has profound consequences for economic theory and for econometric practice. (4) Microeconometrics has contributed substantially to the scientific evaluation of public policy.

This paper examines the argument presented in The Bell Curve. A central argument is that one factor--g--accounts for correlation across test scores and performance in society. Another central argument is that g cannot be manipulated. These arguments are combined to claim that social policies designed to improve social performance cannot be effective. A reanalysis of the evidence contradicts this story. The factors that explain wages receive different weights than the factors that explain test scores. More than g is required to explain either. Other factors besides g contribute to social performance, and they can be manipulated.

In recent years, Congress has considered a variety of work-subsidy programs designed to encourage work among welfare recipients. Many of these programs would subsidize individuals only if they work some minimum number of hours. Commonly used techniques cannot give direct answers to relevant policy questions since a tied offer is involved, and hence the offer cannot be treated as a simple wage change. The essence of the problem involves utility comparisons between two or more discrete alternatives. Such comparisons inherently require information about consumer preferences in a way not easily obtained from ordinary labor-supply functions. To make such comparisons, I present a method for directly estimating consumer indifference surfaces between money income and nonmarket time. Once these surfaces are determined, they can be used to compare a variety of alternative programs to investigate whether or not there is scope for Pareto-optimal redistribution of income transfers and time, improving the general level of welfare of the community at large without reducing the welfare of individuals receiving income transfers. Knowledge of these indifference surfaces allows us to estimate reservation wages to estimate the value of nonworking-women's time (Gronau 1973), laborforce participation functions, hours-of-work functions, and welfare losses due to income tax programs (Harberger 1964). I demonstrate that direct estimation of indifference surfaces allows us, at least in principle, to relax

This paper established that a low dimensional vector of cognitive and noncognitive skills explains a variety of labor market and behavioral outcomes. For many dimensions of social performance cognitive and noncognitive skills are equally important. Our analysis addresses the problems of measurement error, imperfect proxies, and reverse causality that plague conventional studies of cognitive and noncognitive skills that regress earnings (and other outcomes) on proxies for skills. Noncognitive skills strongly influence schooling decisions, and also affect wages given schooling decisions. Schooling, employment, work experience and choice of occupation are affected by latent noncognitive and cognitive skills. We study a variety of correlated risky behaviors such as teenage pregnancy and marriage, smoking, marijuana use, and participation in illegal activities. The same low dimensional vector of abilities that explains schooling choices, wages, employment, work experience and choice of occupation explains these behavioral outcomes.

This paper uses the marginal treatment effect (MTE) to unify the nonparametric literature on treatment effects with the econometric literature on structural estimation using a nonparametric analog of a policy invariant parameter; to generate a variety of treatment effects from a common semiparametric functional form; to organize the literature on alternative estimators; and to explore what policy questions commonly used estimators in the treatment effect literature answer. A fundamental asymmetry intrinsic to the method of instrumental variables (IV) is noted. Recent advances in IV estimation allow for heterogeneity in responses but not in choices, and the method breaks down when both choice and response equations are heterogeneous in a general way.