Discussion Paper 145
Learning Your Earning: Are Labor Income Shocks Really Very Persistent?
Published October 1, 2006
The current literature offers two views on the nature of the labor income process. According to the first view, which we call the “restricted income profiles” (RIP) model, individuals are subject to large and very persistent shocks while facing similar life-cycle income profiles (MaCurdy, 1982). According to the alternative view, which we call the “heterogeneous income profiles” (HIP) model, individuals are subject to income shocks with modest persistence while facing individual-specific income profiles (Lillard and Weiss, 1979). In this paper we study the restrictions imposed by the RIP and HIP models on consumption data—in the context of a life-cycle model—to distinguish between these two hypotheses. In the life-cycle model with a HIP process, which has not been studied in the previous literature, we assume that individuals enter the labor market with a prior belief about their individual-specific profile and learn over time in a Bayesian fashion. We find that learning is slow, and thus initial uncertainty affects decisions throughout the life cycle. The resulting HIP model is consistent with several features of consumption data including (i) the substantial rise in within-cohort consumption inequality, (ii) the non-concave shape of the age-inequality profile, and (iii) the fact that consumption profiles are steeper for higher educated individuals. The RIP model we consider is also consistent with (i), but not with (ii) and (iii). These results bring new evidence from consumption data on the nature of labor income risk.
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