Realized real interest rates, 1920–2015 (interactive) 20% 15% 10% 5% 0% −5% −10% −15% 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 Year Realized real interest rate (%) Shaded years mark realized real rates below zero — 1940s wartime inflation and the 1980 oil-supply shock. −8% 1946 1946: realized real rate ≈ −8%. Unexpected wartime inflation repaid lenders in cheaperdollars — a negative real return they never priced in.