President Trump walks to the White House after arriving on Marine One on March 19. (Alex Brandon/AP)

This story has been updated.

Donald Trump is $1 billion poorer since becoming president, according to Forbes’s latest list of the world’s billionaires.

The magazine’s newest ranking, released Monday, estimated that Trump’s net worth has fallen from $4.5 billion last year to $3.5 billion today, dropping him 220 spots on the magazine’s list of billionaires, from No. 324 last year to No. 544.

Although Trump resigned from his businesses when he entered office, his slide isn’t due to the sale of any of those businesses, because he still owns them.

Rather, Trump’s net worth is down because about 40 percent of his wealth comes from real estate he owns in Midtown Manhattan, including Trump Tower and eight other buildings within about a mile.

“Midtown Manhattan real estate is down; therefore, so is Donald Trump’s fortune,” the magazine said in a statement.

Here's the answer to one of the most Googled questions about Trump. (Osman Malik,Sarah Parnass/The Washington Post)

Trump has disputed Forbes’s estimates in the past, particularly regarding the worth of his brand, which — compared with real estate — is more difficult to value. During the presidential campaign, he said he was worth $8.7 billion, and he said last year in a personal financial disclosure form filed with the federal government that his net worth was “in excess” of $10 billion.

According to its methodology, Forbes bases its billionaires list on a “snapshot of wealth” taken Feb. 17 by valuing assets using stock prices and international exchange rates.

“As we wrote in our cover story on the president’s net worth 18 months ago, Donald Trump has been trying to spin his Forbes valuation for more than three decades. In the early years, editors even joked about the ‘Trump rule’ — take what he claims and divide by three,” said Randall Lane, editor of Forbes Magazine. “Every year Forbes goes through his assets line by line, speaking with dozens of experts about market values — and hearing out Trump and his team. We do not give any credit for ‘brand value’ to Trump or Oprah or any other person on our list — we feel a person’s brand value is already reflected in the income and value of the deals they cut. And we are very comfortable with our estimates for Trump’s tangible holdings, which also factor in things like debt and partnerships, as well as current market conditions.”

All told, Forbes said it was a record year to be rich, as the number of billionaires it counted climbed 13 percent last year to 2,043 from 1,810. The magazine attributed the rise in part to surging stock markets and higher commodity prices.

Microsoft founder Bill Gates leads the list for the fourth year in a row, with a fortune of $86 billion, $11 billion more than last year. Investor Warren Buffett claimed the No. 2 spot, and Amazon chief executive Jeffrey P. Bezos was third (Bezos owns The Washington Post).

Forbes has tracked Trump’s net worth since 1982. A recent breakdown of the president’s wealth valued his New York City real estate at $1.7 billion, his real estate outside New York at $630 million, his golf clubs at $620 million, his cash and personal assets at $270 million, and his brand businesses at $230 million.

As New York’s real estate market slowed, Forbes began downgrading Trump’s net value last year, saying in October that his net worth was down to $3.7 billion.

Forbes isn’t the only publication tracking Trump’s wealth to conclude that he is probably worth much less than he says he is. Fortune and Bloomberg have previously offered their own lower estimates.

Correction: This story was corrected to show that Trump dropped 220 spots on the Forbes list, not 208. 

Follow Jonathan O’Connell on Twitter: @oconnellpostbiz