Under unusual circumstances, investors will settle for lower yields associated with low-risk long-term debt if they think the economy will enter a recession in the near future. For example, the S&P 500 experienced a dramatic fall in mid 2007, from which it recovered completely by early 2013. Investors who had purchased 10-year Treasuries in 2006 would have received a safe and steady yield until 2015, possibly achieving better returns than those investing in equities during that volatile period.

Economist Campbell Harvey's 1986 dissertation showed that an inverted yield curve accurately forecasts U.S. recessions. An inverted curve has indicated a worsening economic situation in the future eight times since 1970.

In addition to potentially signaling an economic decline, inverted yield curves also imply that the market believes inflation will remain low. This is because, even if there is a recession, a low bond yield will still be offset by low inflation. However, technical factors, such as a flight to quality or global economic or currency situations, may cause an increase in demand for bonds on the long end of the yield curve, causing long-term rates to fall. Falling long-term rates in the presence of rising short-term rates is known as "Greenspan's Conundrum".
Extract the reasons why inverted yield curve could happen, and place them in a bullet list.
There are two reasons why an inverted yield curve could happen
1. When investors think the economy will enter a recession in the near future, they will settle for lower yields associated with low-risk long-term debt, which would likely result in higher returns than investments in equities during the same time.
2. When the market believes inflation will remain low, there will be more demand for bonds on the long end of the yield curve, causing long-term rates to fall.