Measuring the US social discount rate

The purpose of this letter is to estimate the US social discount rate, the appropriate discount rate for public capital budgets. There are two methods. One assumes that public investment displaces private consumption, and the discount rate is labelled the social rate of time preference (SRTP). The other assumes that public investment crowds out private investment, and the underlying social discount rate is market-based. The approach in this letter follows the second method. It relies on wealth maximization with the presence of two assets: one risky and one riskless. The risky security is taken to be a portfolio of common stocks, while the riskless asset is taken to be the T-bill rate. The Euler or first-order condition is independent of initial wealth. Because of that the estimate of the discount rate applies to all unanimously, and can be considered a social rate by essence. The range of the estimated social discount rate is between 5.01% and 6.17%, and the 95% confidence interval for the inferred population mean discount rate is between 5.62% and 5.71%. These results are extremely precise and reasonable, and are at the upper limit of the estimates in the literature that use a completely different approach.