Knowledge that Transforms

The paper examines the effects of the composition of unemployment on wage determination. It explores the implication of one central assumption: when firms receive multiple acceptable applications, they hire the worker who has been unemployed for the least amount of time. This assumption (“ranking”) is contrasted with the assumption of random hiring (“no-ranking”). By embodying this assumption in a model of the labour market with job creation/destruction and matching, the joint behaviour of unemployment, the distribution of unemployment durations, and wages are characterized. The implication that the re-employment prospects of employed workers, were they to become unemployed, are better than those of the currently unemployed appears to have been an important feature of European unemployment experience in the 1980's.

Changes in variance, or volatility, over time can be modelled using the approach based on autoregressive conditional heteroscedasticity (ARCH). However, the generalizations to multivariate series can be difficult to estimate and interpret. Another approach is to model variance as an unobserved stochastic process. Although it is not easy to obtain the exact likelihood function for such stochastic variance models, they tie in closely with developments in finance theory and have certain statistical attractions. This article sets up a multivariate model, discusses its statistical treatment and shows how it can be modified to capture common movements in volatility in a very natural way. The model is then fitted to daily observations on exchange rates.

Investment is often irreversible: once installed, capital has little or no value unless used in production. This paper proposes and solves a model of sequential irreversible investment and characterizes the aggregate implications of microeconomic irreversibility and idiosyncratic uncertainty. If a large amount of idiosyncratic uncertainty is allowed for, the distributional dynamics induced by the nonlinear character of irreversible investment policies are capable of smoothing the dynamics of aggregate investment (relative to those of its forcing processes) to the extent required by U.S. data.