Income Mobility and Welfare∗

This paper develops a framework for the quantitative analysis of individual income dynamics, mobility and welfare. Individual income is assumed to follow a stochastic process with two (unobserved) components, an i.i.d. component representing measurement error or transitory income shocks and an AR(1) component representing persistent changes in income. We use a tractable consumption-saving model with labor income risk and incomplete markets to relate income dynamics to consumption and welfare, and derive analytical expressions for income mobility and welfare as a function of the various parameters of the underlying income process. The empirical application of our framework using data on individual incomes from Mexico provides striking results. Much of measured income mobility is driven by measurement error or transitory income shocks and therefore (almost) welfare-neutral. A smaller part of measured income mobility is due to either welfare-reducing income risk or welfare-enhancing catching-up of lowincome individuals with high-income individuals, both of which have economically significant effects on social welfare. Decomposing mobility into its fundamental components is thus seen to be crucial from the standpoint of welfare evaluation. ∗We are grateful to seminar participants at Columbia, Harvard and Pennsylvania State University for many useful comments. Particular thanks to Francois Bourguignon, Francisco Ferreira, Gary Fields, and the other participants at the World Bank/Universitat Autonoma de Barcelona Workshop on Mobility for very helpful discussions. Our appreciation to Edwin Goni and Mauricio Sarrias for inspired research assistance. This work was partially supported by the Regional Studies Program of the Office of the Chief Economist for Latin America and the World Bank Research Support Budget.