We study the effects of permanent and temporary income shocks on precautionary saving and investment in a "store-or-sow" model of growth. High volatility of permanent shocks results in high precautionary saving in the safe asset and low investment, or a "volatility trap." Namely, big savers invest relatively little. In contrast, low volatility of permanent shocks leads to low precautionary saving and high or low investment, depending on the volatility of temporary shocks. Empirical evidence shows a nonlinear relationship between investment and saving and that investment is a hump-shaped function of the volatility of permanent shocks, as predicted by the model.

One of the basic motives for saving is the accumulation of wealth to insure future welfare. Both introspection and extant research on consumption insurance find that people face substantial risks that they do not fairly pool. In theory, the consumption and wealth accumulation of price-taking households in an economy with incomplete markets differs substantially from the behavior of these same households in the equivalent economy with complete-markets. The question we address in this article is whether we find this difference to be large in practice. What is the empirical importance of precautionary saving? We provide a simple decomposition that characterizes the importance of precautionary saving in the U.S. economy. We use this decomposition as an organizing framework to present four main findings: (a) the concavity of the consumption policy rule, (b) the importance of precautionary saving for life-cycle saving and wealth accumulation, (c) the contribution of changes in risk to fluctuations in aggregate consumption and (d) the significant impact of incomplete markets on aggregate fluctuations in calibrated general equilibrium models. We conclude with directions for future research.

We argue that the U.S. personal saving rate’s long stability (from the 1960s through the early 1980s), subsequent steady decline (1980s - 2007), and recent substantial increase (2008 - 2011) can all be interpreted using a parsimonious ‘buffer stock’ model of optimal consumption in the presence of labor income uncertainty and credit constraints. Saving in the model is affected by the gap between ‘target’ and actual wealth, with the target wealth determined by credit conditions and uncertainty. An estimated structural version of the model suggests that increased credit availability accounts for most of the saving rate’s long-term decline, while fluctuations in net wealth and uncertainty capture the bulk of the business-cycle variation.

How does financial integration impact capital accumulation, current-account dynamics, and cross-country inequality? This paper investigates this question within a two-country, general-equilibrium, incomplete-markets model that focuses on the importance of idiosyncratic entrepreneurial risk -- a risk that introduces, not only a precautionary motive for saving, but also a wedge between the interest rate and the marginal product of capital. This friction provides a simple resolution to the empirical puzzle that capital often fails to flow from the rich or slow-growing countries to the poor or fast-growing ones, and a distinct set of policy lessons regarding the intertemporal costs and benefits of capital-account liberalization. Illus. A print on demand report.