Before Mr. Trump became president, his investment accounts at Deutsche Bank and Barclays were stuffed with blue-chip stocks, which have been decimated this year. When he closed those accounts, his only exposure to the stock and bond markets was through three family trusts. The investments in those trusts are managed by an outside trustee, not by Mr. Trump.

Mr. Trump’s last financial disclosure form was filed in May. The form listed the specific funds in which the three Trump trusts had money, but it provides only ranges of the amount invested in each fund, not precise values. It’s possible that money has been added or withdrawn from those accounts since then.

But last spring, Mr. Trump had somewhere between $597,000 and $2.4 million in the markets through the three trusts. If those holdings were unchanged, Mr. Trump has lost somewhere between $97,705 and $360,246 this year.

Those losses would barely dent Mr. Trump’s fortune. In addition to his extensive real estate holdings, worth hundreds of millions of dollars, he reported having at least $47 million in several checking, savings and money-market accounts. (That is offset by the hundreds of millions of dollars that Mr. Trump owes to Deutsche Bank and other financial institutions.)

The White House didn’t respond to a request for comment.

Before the S&P 500 soared more than 9 percent on Friday, as Mr. Trump declared a national emergency because of the coronavirus, his investments were slightly beating the broader market. They were down between 18 percent and 21 percent for the year, while the S&P 500 was down 23 percent.