The real interest rate is calculated as the difference between the nominal interest rate and the inflation rate. The chart above displays the nominal interest rate of a 1-year US Treasury bond, the US inflation rate, and the resulting one-year real interest rate. Inflation is defined as the yearly percentage change of the Consumer Price Index (CPI). When inflation is high, prices for goods and services rise and thus the purchasing power per unit of currency decreases. The chart shows that, adjusted for inflation, the yields on US Treasuries (blue line) have often been negative.
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