The purpose of this paper is to summarize a certain line of work on
the interpretation of unemployment in the analysis of male labour supply
behavior. Specifically, this work investigates whether the data support
the null hypothesis that individuals experiencing unemployment are on a
labour supply function, and if the data do not support this hypothesis,
how might a researcher proceed in empirical work. The motivation for
doing this is two fold. First, what unemployment represents is an
intrinsically interesting question, and may have implications beyond
labour supply analysis in terms of macroeconomic theory. Second, if
unemployed workers are constrained in the sense that they are off their
individual labour supply functions, standard labour supply estimation
may involve a fundamental misspecification of the equation. However, it
should be emphasized that the purpose of this paper is to survey one
possible approach to this problem; the paper does not attempt to provide
a general survey on labour supply estimation or on constraints in the
labour market.

This study proposes and implements a specification test for the
hypothesis that unemployment represents intertemporal labour supply
behavior. The test allows for uncertainty and endogenous unemployment.
Given standard specifications of the intertemporal labour supply model, I
find strong evidence against this interpretation of unemployment. These
results indicate the need to turn to either 1) alternative models where
unemployed workers are off a supply function or ii) more complex models
of intertemporal substitution.