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.
Historically, the real interest rate on ten-year Treasuries has been above 2%; thus, today’s rate is about two percentage points below its historical average. But those historical rates prevailed at times when fiscal deficits and federal government debt were much lower than they are today. With budget deficits that are projected to be 5% of GDP by the end of the coming decade, and a debt/GDP ratio that has roughly doubled in the past five years and is continuing to grow, the real interest rate on Treasuries should be significantly higher than it was in the past.
The reason for today’s unsustainably low long-term rates is not a mystery. The Federal Reserve’s policy of “long-term asset purchases,” also known as “quantitative easing,” has intentionally kept long-term rates low. The Fed is buying Treasury bonds and long-term mortgage-backed securities at a rate of $85 billion a month, equivalent to an annual rate of $1,020 billion. Since that exceeds the size of the government deficit, it implies that private markets do not need to buy any of the newly issued government debt.