We consider the sensitivity of the Tobit estimator to heteroscedasticity. Our single independent variable is a dummy variable whose coefficient is a difference between group means, and the error variance differs between groups. Heteroscedasticity biases the Tobit estimate of the two means in...

In this paper we draw attention to two problems associated with the use of instrumental variables (IV) whose importance for empirical work has not been fully appreciated. First, using potential instruments that explain little of the variation in the: endogenous explanatory variables can lead to...

Investigators of social differentials in health outcomes commonly augment incomplete micro data by appending socioeconomic characteristics of residential areas (such as median income in a zip code) to proxy for individual characteristics. However, little empirical attention has been paid to how...

Under stationarity, the heterogeneous stoahastic processes are the non-ergodic ones. We show that if a distributed lag is of finite order, then its coefficients are unconditional means of the underlying random coefficients. This result is applied to linear transformations of the process. The...

This document describes the panel of publicly traded United States manufacturing firms which was created and updated at the National Bureau of Economic Research from 1978 through 1988 within the Productivity Program. The panel consists of about 2600 large manufacturing firms with three to...

We use a simple graphical approach to represent Social Welfare Functions that satisfy Independence of Irrelevant Alternatives and Anonymity. This approach allows us to provide simple and illustrative proofs of May's Theorem, of variants of classic impossibility results, and of a recent result on...

A common feature to most aggregative studies of the labor market is a marginal productivity expression in which the quantity of labor appears on the left hand side of the equation, and the right hand side includes the real wage and output. A number of researchers have cautioned that if the...

Do studies of time use interfere too much in the lives of the subjects? As a result are those who agree to participate a biased sample of the population? We examine the characteristics of the Experience Sampling Method (ESM) adolescent sample from the Alfred P. Sloan Study of Youth and Social...

This paper introduces a limited-information two-step estimator for models with rational expectations and serially correlated disturbances. The estimator greatly extends the area of applicability of McCallum's (1976) instrumental variables approach to rational expectations models. Section I...

The paper investigates the robustness of the proposition that in stochastic models contingent or feddback rules dominate fiped or openloop rules. Four arguments in favour of fixed rules are considere`. 1) The presence of an incompetent op malevolent policy maker. 2) A trade-off between...