By Greg Kaplan and Giovanni Violante
A wide body of empirical evidence, based on randomized experiments, finds that 20-40 percent of fiscal stimulus payments (e.g. tax rebates) are spent on nondurable household consumption in the quarter that they are received. We develop a structural economic model to interpret this evidence. Our model integrates the classical Baumol-Tobin model of money demand into the workhorse incomplete-markets life-cycle economy. In this framework, households can hold two assets: a low-return liquid asset (e.g., cash, checking account) and a high-return illiquid asset (e.g., housing, retirement account) that carries a transaction cost. The optimal life-cycle pattern of wealth accumulation implies that many households are “wealthy hand-to-mouth” : they hold little or no liquid wealth despite owning sizeable quantities of illiquid assets. They therefore display large propensities to consume out of additional income. We document the existence of such households in data from the Survey of Consumer Finances. A version of the model parameterized to the 2001 tax rebate episode is able to generate consumption responses to fiscal stimulus payments that are in line with the data.
The extant literature exploits the timing of the mailing of the stimulus checks to determine the marginal propensity to consume. But all recipients were expecting those checks to come, so what is measured is really the impact of differences in liquidity. What Kaplan and Violante do is build a realistic model of liquidity management that yields the measured predictions in order to back out from the model what the true propensity to consume is. A very subtle exercise.