A Greenwich resident, he is ranked 92nd globally with a net worth of $13 billion.
While Mr. Trump's political fortunes were rising, his net worth was dropping to a mere $3.5 billion, or roughly a third of what he claimed during his successful campaign for the USA presidency, according to the latest Forbes list of the world's billionaires.
The total number of women on the list is 227, up from 202 in 2016.
The collective worth of all the men and women on the Forbes list is US$7.67 trillion, up from US$6.48 trillion in 2016.
Facebook founder Mark Zuckerberg moved up to number five for the first time, after his fortune rose $11.4 billion in 12 months.
While Gates' pal Warren Buffett took over the No. 2 spot at $75.6 billion, it was Amazon founder and CEO Jeff Bezos who had the best year of anyone.
Whilst the US President has refused to publish any of his tax returns to show the true scale of his wealth, during his Presidential campaign he claimed he was worth "an excess of $10 billion". His latest ranking reflects a dip of about $1 billion, by Forbes' reckoning. For the second year running France's Liliane Bettencourt, the L'Oreal cosmetics heiress, was the world's wealthiest woman with a $39.5bn net worth.
Mr. Trump previously has labeled media reports about the inquiry as "fake news".
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.
Elsewhere in the rankings, financial magnates with local origins and business leaders associated with Massachusetts-based companies were among the record 2,047 billionaires on this year's list.
Ortega's fortune was up $4.3 billion since a year ago, but he still fell to fourth in the world, unable to keep up with the outsize gains of others. I'm worth much more than you have me down [for].
He is listed by Forbes as a U.S. citizen, but became a New Zealand citizen six years ago.
For the fourth consecutive year, Microsoft co-founder and philanthropist Bill Gates topped this year's rich with an estimated fortune of around $86bn.