David A. Andelman is a visiting scholar at the Center on National Security at Fordham Law School and director of its Red Lines Project. He also is a contributor to CNN and a columnist for USA Today, and author of "A Shattered Peace: Versailles 1919 and the Price We Pay Today." He was a foreign correspondent for The New York Times and CBS News in Asia and Europe. Follow him on Twitter @DavidAndelman. The views expressed in this commentary are his.

(CNN) Donald Trump is suddenly learning a very hard lesson. Stock markets that go up can, quite suddenly and precipitously, go down. And then there's the other half of that lesson. When you buy the good news, you inevitably own the bad as well.

That's the stunning conclusion from Monday's largest single-day drop in the history of the Dow Jones Industrial Average -- 1,175 points in one day, or 1,841 points in the last two trading days. In percentage terms, that's the biggest drop since the 2008 financial crisis.

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For the major indexes, Monday's market plunge wipes out the entire gain for this year -- a gain the President pats himself on the back for almost every day. For perspective, more than a trillion dollars in total value has been wiped off the books and out of the hands of American investors, retirees and anyone with a 401(k) or IRA.

There's more to this than meets the eye. It's also the first day on the job of the new chairman of the Federal Reserve, after a weekend when his predecessor, Janet Yellen, let it be known she was most disappointed in not getting a second term from Donald Trump. The markets might have wanted to have a more experienced hand on the tiller at the moment.

It was quite a roller-coaster day, one that tries even the most stolid souls. But Trump, who spent the afternoon in Blue Ash, Ohio, trumpeting his economic and tax plan and all it is doing for the average American, did not say a single word on what was happening 650 miles to the east at the New York Stock Exchange.

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