CAMBRIDGE – Long-term interest rates are now unsustainably low, implying bubbles in the prices of bonds and other securities. When interest rates rise, as they surely will, the bubbles will burst, the prices of those securities will fall, and anyone holding them will be hurt. To the extent that banks and other highly leveraged financial institutions hold them, the bursting bubbles could cause bankruptcies and financial-market breakdown.
The very low interest rate on long-term United States Treasury bonds is a clear example of the current mispricing of financial assets. A ten-year Treasury has a nominal interest rate of less than 2%. Because the inflation rate is also about 2%, this implies a negative real interest rate, which is confirmed by the interest rate of -0.6% on ten-year Treasury Inflation Protected Securities (TIPS), which adjust interest and principal payments for inflation.