Trump values unpredictability. He also values rising markets. He can’t have both.

President Trump at a signing ceremony in the Eisenhower Executive Office Building in Washington on Dec. 20. (Jabin Botsford/The Washington Post) December 27 at 11:33 AM

The Dow has been swinging hard lately. The widely watched industrial average fell by more than 350 points for three consecutive days to end last week, then dropped 653 points on Monday. It was closed Tuesday. Wednesday, it was back up 1,086 points.

President Trump, who famously used unpredictability in his career as a real estate developer and self-proclaimed dealmaker, probably did not want to apply that word to his effect on the stock market. For much of his tenure, he has taken credit for stock market gains.

But by multiple measures, the market’s future seems less certain now than at any time since Trump’s election. It’s hard to know how much can be directly tied to him. The market has been climbing for a long time, and the Federal Reserve’s interest rate hikes, while expected, may be muddying the outlook. It’s hard to conclude, though, that Trump, with his trade war, White House crises and criticism of the Fed, is a force for certainty.

And a large body of economic research shows that the type of uncertainty that worked for one business executive won’t do the same for the economy at large.

When the future is uncertain, businesses tend to hire less and invest less in the equipment, people and innovations that become the foundation for long-term economic growth.

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