Credit cycle is one reason. Low interest rates mean higher bond prices (this is an inherent attribute of debt pricing, look at pricing of high yield debt the la

Credit cycle is one reason. Low interest rates mean higher bond prices (this is an inherent attribute of debt pricing, look at pricing of high yield debt the last few years vs fed funds rate as an example), lower interest rates also lead to lower expected return / higher stock prices (CAPM), and higher interest rates lead to falls in those prices When interest rates are low and money is cheap, people take on more debt. Investors also invest in riskier assets because more money is available and competition for assets is greater. Eventually, default rates rise as there are more bad credits, and equity markets build up a lot of negative "potential energy" as prices rise based on increasing money supply. When interest rates rise, the reverse happens This is probably not exactly what you were looking for, but it's one reason why we have cycles