Fluctuation in Equilibrium Unemployment

Fluctuations in the equilibrium rate of unemployment can only be understood within a theory of the natural or equilibrium rate. It is not enough to say that unemployment is the difference between supply and demand in the labor market, though of course it always will be. In equilibrium, no participants in the market can have an unexploited opportunity to make themselves better off. At the equilibrium unemployment rate, employers cannot obtain labor at lower cost by offering work at below the market wage to the unemployed. Unemployed workers cannot raise their effective real incomes by taking lower wages in exchange for immediate employment. The task of the theory is to explain why any unemployment remains at all when these conditions are satisfied. Part of this problem has been studied in detail in the "search theory" of unemployment -- once a worker becomes unemployed, it is reasonably well understood why the worker does not become employed again immediately. The theory of why people become unemployed in the first place is less well developed and is the main concern of this paper. Most of the unemployed are looking for new work because their previous jobs ran out. Consequently, the main ingredient of a theory of the flow of workers into unemployment is a theory of the duration of employment. Such a theory is developed here, along reasonably standard lines.