Taking advantage of key recent advances in long-run economic and financial data, we analyze the statistical properties of global long-maturity real interest rates over the past seven centuries. In contrast to existing consensus, we find that real interest rates are in fact trend stationary and exhibit a persistent downward trend since the Renaissance. We investigate structural breaks in real interest rates over time and find that overall the Black Death and the 1557 “Trinity default” appear as consistent inflection points. We further show that demographic and productivity factors do not represent convincing drivers of real interest rates over long spans.

We show that “commodity currency” exchange rates have surprisingly robust power in predicting global commodity prices, both in-sample and out-of-sample, and against a variety of alternative benchmarks. This result is of particular interest to policy makers, given the lack of deep forward markets in many individual commodities, and broad aggregate commodity indices in particular. We also explore the reverse relationship (commodity prices forecasting exchange rates) but find it to be notably less robust. We offer a theoretical resolution, based on the fact that exchange rates are strongly forward-looking, whereas commodity price fluctuations are typically more sensitive to short-term demand imbalances.