Dumb money is pejoratively a reference to retail investors (and also the title of the movie about the surge in GameStop stock). Basically, mom and pop usually arrive late to any investment news and end up being the exit liquidity for the professionals. That is not universally the case - in the GameStop situation, for instance, a major hedge fund was driven out of business - but the professionals usually have the upper hand.

If there's a group even dumber, unfortunately, it would be foreign retail investors. And they're buying U.S. stocks like they're going out of fashion.

Ed Yardeni, president of Yardeni Research, crunched the numbers and found foreigners purchasing U.S. equities at a record pace of $76.5 billion over the last three months. The chart tells the story: non-Americans have absolutely awful timing with regard to U.S. stocks, buying right before the 1987 crash, the bursting of the dot-com bubble in 2000, and the 2008 global financial crisis.

As he puts it: "Their buying has a record of being a contrary indicator. They tend to be big buyers right before bear markets," he wrote.

The Financial Times interviewed some of them earlier this month, for a story about South Korean holdings of U.S. stocks surging 65% last year.

Their logic is reasonable enough: the U.S. market has been home to the corporate winners, the likes of Apple, Nvidia and Tesla, while the local companies struggle to compete.

That pattern has been repeated throughout the world. In the U.K. in November, for instance, retail inflows into U.S. stock-market funds were GBP590 million while domestic equity funds saw outflows of GBP552 million, according to the Investment Association, a local trade group.

It's not just the great unwashed buying American stocks: the suits are too. Historian Niall Ferguson was at the Davos conference this week. "Almost everyone at the World Economic Forum in Davos, Switzerland is long United States, short European Union," he wrote for the Free Press. "The new Davos consensus is that Europe cannot get its economic act together and never will, whereas America is rocking and rolling, and if you don't own the big U.S. stocks, then the [fear of missing out] may kill you," he said.

"The trouble is that the Davos consensus is nearly always wrong," he said.

Being contrarian for contrarian's sake is not necessarily a winning strategy. Yardeni, for instance, is nonetheless one of the most bullish strategists on Wall Street. But in this case, there's a big valuation argument supporting the contrarians.

The iShares MSCI all-country index ex U.S. ETF ACWX has a forward price-to-earnings ratio of 13.4, while the SPDR S&P 500 ETF trust SPY has a forward price-to-earnings ratio of 22.1, according to FactSet.