U.S. public debt has more than doubled over the past 25 years, potentially posing consequences for fiscal and monetary policy through its effect on inter est rates. Standard theory predicts that higher debt crowds out productive cap ital, pushing rates up, but existing empirical estimates are typically static and ignore how the level of existing debt along with the composition and timing of debt-financed policies influence these effects. Using a heterogeneous agent life cycle model that is richly calibrated to U.S. household behavior, we show that there is significant variation in the dynamic interest rate responses across differ ent debt-financed policies. […]