The narrow public ownership of equities limits the spending impulse for consumers, but the high equity valuations offer companies a huge collateral buffer to borrow. US nonfinancial companies are sitting on over $10 trillion in debt, almost twice as much as what was on corporate balance sheets at the end of 2008, and the highest debt-to-sales ratio on record.
From many sides, monetary policy nowadays stimulates finance more than spending and as the equity market goes so goes the business cycle.