According to the normal bond investment theory, the more depressed the economy is, the lower the yield of government bonds will be (except for non-government bonds, corporate bonds will also be affected by their own operating factors, depending on the specific situation). Investors have no confidence in the future, but their lack of confidence mainly lies in the fact that they can't find a good investment channel when the economy goes down, and investing in the real economy or enterprises will face high investment risks, which is almost risk-free investment for government bonds. Investing in national debt can obtain stable investment income. When investors can't find a low-risk investment channel in the economic downturn, national debt investment is the first choice, and funds will chase national debt, which will increase the price of national debt and decrease the yield (the bond price is inversely proportional to the yield). Actually, there is another reason. In the case of economic depression, various methods or means are often used to stimulate the economy, and monetary policy is one of them. Monetary policy tends to be loose (loose monetary policy can be seen in quantitative easing in the United States, which provides a lot of cheap funds to the market) or interest rate reduction will cause the market interest rate to fall, and the decline in market interest rate will also be transmitted to the yield of the national debt market, which is reflected in the decline in yield.

As the yield to maturity of national debt in the market declines, it will force the coupon rate of bonds issued in the primary market to decline, so entering the economic recession will lead to the decline of long-term bond interest rates. In fact, excluding the credit risk, the bond interest rate or yield to maturity is often positively related to the economic situation.