Pointing to data showing run-ups in foreign purchases of U.S. stocks before the 1987 crash, the dot-com bubble in 2000, and the 2008 financial crisis, Ed Yardeni wrote in his eponymous research newsletter, "Their buying has a record of being a contrary indicator. They tend to be big buyers right before bear markets."

The U.S. stock market has gone taken a nosedive since President Donald Trump announced tariffs for many countries around the world. Here's what to know.

The Fed chief warns higher inflation is likely, although officials routinely say their outlook depends on how Trump’s policies — on trade, immigration and more — shake out.