Learning Your Earning: Are Labor Income Shocks Really Very Persistent?

The current literature offers two views on the nature of the income process. According to the first view, which we call the “restricted income profiles” (RIP) model (MaCurdy, 1982), individuals are subject to large and very persistent shocks, while facing similar life-cycle income profiles (conditional on a few characteristics). According to the alternative view, which we call the “heterogeneous income profiles” (HIP) model (Lillard and Weiss, 1979), individuals are subject to income shocks with modest persistence, while facing individual-specific income profiles. While labor income data does not seem to distinguish between the two hypotheses in a definitive way, the RIP model is overwhelmingly used to specify the income process in economic models, because it delivers implications consistent with certain features of consumption data. In this paper we study the consumption-savings behavior under the HIP model, which so far has not been investigated. In a life-cycle model, 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 allowing us to estimate the prior uncertainty from consumption behavior later in life. This procedure implies that 40 percent of variation in income growth rates is forecastable by individuals at time zero. The resulting model is consistent with several features of consumption data including (i) the substantial rise in within-cohort consumption inequality (Deaton and Paxson 1994), (ii) the non-concave shape of the age-inequality profile (which the RIP model is not consistent with), and (iii) the fact that consumption profiles are steeper for higher educated individuals (Carroll and Summers 1991). These results bring new evidence from consumption data on the nature of labor income risk.