Knowledge that Transforms

This paper establishes that when there is not a complete set of markets but more than one commodity the stock market equilibrium will not in general be a constrained Pareto optimum. The economy will lack both the property of exchange and production efficiency. Necessary conditions which must be satisfied if the economy is to be a constrained Pareto optimum for all technologies are derived; if all individuals have identical, homothetic indifference maps, then either there must be unitary price elasticities (so there is no effective risk) or all individuals must have the same degree of risk aversion (so there is no trade on the stock market).

Lancaster and Nickell (1980) have argued that in the proportional hazard model the effects of time dependence (true duration dependence) and unobserved sample heterogeneity (spurious duration dependence) cannot be distinguished. We show that both effects can be distinguished if the model allows for observed explanatory variables in the hazard. We also discuss the application of our result to practical situations.

This article addresses the issue of specification of econometric selectivity models and suggests approaches for the correction of selectivity bias. Our approaches provide ways to specify selectivity models without the assumption of multinormal distribution. Some flexible function forms for the correction of selectivity bias in the regression equation are derived. All the models considered can be estimated by simple consistent two stage methods. Our approaches provide simple procedures for the testing of selectivity bias without imposing restrictive distributional assumptions and also tests for the normality assumption.

The literature on inequality measurement has been largely concerned with single-dimensioned indicators. This paper explores some of the issues which arise when there are several dimensions to inequality, and these are not readily reduced to a single index, concentrating particularly on the two-dimensioned case. We make use of results on multi-variate stochastic dominance in portfolio theory, extending these and applying them to the measurement of inequality. The use of the dominance conditions is illustrated by an application to the international distribution of income and life expectancy.

A dynamic, equilibrium model of long term (implicit) labour contracts under incomplete but symmetric information is developed. Workers are assumed to be risk averse and of unknown ability or productivity. Risk neutral firms learn, as do workers, about each worker's productivity by observing the worker's output over time. It is shown that equilibrium contracts provide for wages which never decline with age and increase only when the worker's market value increases above his current wage. In addition to characterizing the equilibrium wage contract, we also derive some of its implications for the behaviour of aggregate wages across various groups of workers. These implications explain some findings in the recent empirical literature on age-earnings profiles. In particular our model can explain why earnings may be positively related to experience even after controlling for productivity, as some empirical studies have indicated.

This paper generalizes the Durbin-Watson type statistics to test the OLS residuals from the fixed effects model for serial independence. Also generalized are the tests proposed by Sargan and Bhargava for the hypothesis that the residuals form a random walk. A method for efficient estimation of the parameters is also developed. Finally, an earnings function is estimated using the Michigan Survey of Income Dynamics in order to illustrate the uses of the tests and the estimation procedures developed in this paper.

Using a simple search technology and the Nash bargaining solution, the paper derives the steady state equilibrium negotiated wage as a function of the equilibrium unemployment and vacancy rates. For this wage, the lifetime expected present discounted value of earnings of a new worker is compared with the social marginal product of a new worker. These are not generally equal implying inefficient incentives for labour mobility.

This paper studies the consequences for the behaviour of aggregate output of the perception on the part of firms that changing prices is costly. The rational expectations equilibrium of an economy with many such firms is constructed. It is shown that in this economy nominal shocks have a persistent effect on aggregate output. Furthermore, the real wage is demonstrated to move procyclically in such an economy.

The notion of a Perfect Equilibrium in a multi-stage game is used to characterize industry equilibrium under Monopolistic Competition, where products are differentiated by quality.