Fed Chair Janet Yellen says the current high stock market valuation does not mean overvaluation. A stock market quick fire sale would pose minimal risk to the economy and the macroprudential system. During her final Federal Reserve press conference, Yellen says the prime metrics such as the forward aggregate stock market P/E and P/B ratios are on the high end of historical ranges when the Fed warns that asset prices appear to be high. In fact, the low-interest-rate economic environment is supportive of higher stock prices and home prices. In this context, there is a reasonable balance of financial risks that manifest in the form of less worrisome levels of both bank leverage and private credit growth.

A recent Project Syndicate op-ed article sketches the key reasons for U.S. stock market rational exuberance such as better economic growth with low inflation, monetary and fiscal stimulus, full employment, and higher net income in both the household and corporate sectors. As the world economy skyrockets on all cylinders in America, Europe, and China with robust economic growth since the global financial crisis of 2008-2009, U.S. inflation remains below the 2% target, unemployment is less than 5%, and monetary policy normalization continues at a moderate pace. Federal Reserve shrinks its balance sheet post-QE, finishes the full course of 3 interest rate hikes in 2017, and then expects another around of 3 to 4 rate increases in 2018. The current 7-year uptick in U.S. corporate net income typically precedes the European and Asian counterparts in subsequent episodes. All of these reasons help justify the current Trump stock market rally as rational exuberance and optimism.