3. Monetary policy

The Federal Reserve set interest rates near zero in the wake of the financial crisis, and they have stayed historically low ever since. When rates are low, it makes money cheap for businesses, which use it to make acquisitions, repurchase their own shares, and invest in research and development to continue to grow — all things that drive future earnings and stock market returns.

Low rates look poised to continue. On Tuesday, the Federal Reserve handed down a half-percentage point emergency interest rate cut amid market volatility due to the coronavirus outbreak.