We solve each household's optimal saving decisions using a life cycle model that incorporates uncertain lifetimes, uninsurable earnings and medical expenses, progressive taxation, government transfers, and pension and social security benefits. With optimal decision rules, we compare, household by household, wealth predictions from the life cycle model using a nationally representative sample. We find, making use of household-specific earnings histories, that the model accounts for more than 80

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... ercent of the 1992 cross-sectional variation in wealth. Fewer than 20 percent of households have less wealth than their optimal targets, and the wealth deficit of those who are undersaving is generally small.