A particularly famous efficiency-wages model was the one devised by Shapiro & Stiglitz (1984) - a ‘shirking’ model. The main assumption is that there is imperfect, asymmetric information and that workers have a choice to work or ‘shirk’ (exert little or no effort) and that there is a probability that employers catch them and that they don’t catch them. From this simple assumption, Shapiro & Stiglitz conclude that the wage-rate paid in the market will be an efficiency-wage that is higher than the market-clearing wage. The model predicts that there will necessarily be involuntary unemployment in equilibrium which supposedly acts as a ‘worker discipline device’ since it discourages workers from shirking because their being fired would mean that there is a possibility that they may not find another job. For those who are interested in a graphical representation, the graph below depicts the Aggregate Labour Demand (ALD) curve, the Aggregate Labour Supply curve (ALS – which also presumes a competitive labour supply), the Non-Shirking Condition (NSC) and the Efficiency Wage (EW) at equilibrium. Several of the underlying assumptions can be challenged, however. For example, since the state of technology enters the Aggregate Labour Demand relation and the state of technology is not static but it actually improves over time, when we take a dynamic view of the Shapiro-Stiglitz model, we find that the positive technology shocks consistently shift the ALD curve outward.
Furthermore, Shapiro & Stiglitz make a simplifying assumption that the worker believes the likelihood of finding another job (if fired) is equivalent to the proportion of unemployed people – this simplification means that, at the limit of full employment, the Non-Shirking Condition (NSC) cannot intersect with the Aggregate Labour Supply (ALS) – this means that full employment is a theoretical impossibility. In reality, however, people have individualised estimates with respect to how likely they are to get another job if they are fired (based, for example, on their estimation of their own ability, how well their skills match to vacancies and other variables) – this more realistic assumption makes full employment possible.
Remember, how the Aggregate Labour Demand curve experienced constant positive technology shocks over time? Well, this subsequently means that there would be full employment since the NSC and the ALD would intersect at or beyond the ALS curve as time progressed. However, the outcome of full employment here presumes static population growth. In reality, the population changes over time (generally, the ALS might shift right over time to signify an increase in the population over time) and, because of this, the conclusion of the model becomes ambiguous.
Simplified models yield nice conclusions whilst more complex models yield ambiguous results. With Shapiro & Stiglitz’s initially realistic assumption, one may have thought that involuntary unemployment was going to be an inevitable labour market outcome even in a competitive labour market. However, when relaxing the accompanying unrealistic assumptions, it’s not so straightforward.