Financial commentators have called for more research on sustainable spending rates for individuals and endowments holding diversified portfolios. We present a forward-looking framework for analyzing spending rates and introduce a simple measure, stochastic present value, that parsimoniously meshes investment risk and return, mortality estimates, and spending rates without resorting to opaque Monte Carlo simulations. Applying it with reasonable estimates of future returns, we find payout ratios should be lower than those many advisors recommend. The proposed method helps analysts advise their clients how much they can consume from their savings, whether they can retire early, and how to allocate their assets.