What happens to stocks and cryptocurrencies when the Fed stops raining money?

To veterans of financial bubbles, there is plenty familiar about the present. Stock valuations are their richest since the dot-com bubble in 2000. Home prices are back to their pre-financial crisis peak. Risky companies can borrow at the lowest rates on record. Individual investors are pouring money into green energy and cryptocurrency.

This boom has some legitimate explanations, from the advances in digital commerce to fiscally greased growth that will likely be the strongest since 1983.

But there is one driver above all: the Federal Reserve. Easy monetary policy has regularly fueled financial booms, and it is exceptionally easy now. The Fed has kept interest rates near zero for the past year and signaled rates won’t change for at least two more years.