CEO Abigail Johnson of Boston-based Fidelity Investments has a net worth of $14.4 billion and ranked 75th on Forbes' list.
"Midtown Manhattan real estate is down; therefore, so is Donald Trump's fortune", the business magazine said in a statement.
The total worth of people on the list amount to a huge £6.18 trillion - more than double the UK's annual gross domestic product.
Last year, Forbes said Trump was the 324th-richest person in the world.
While Donald 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 US presidency, according to the latest Forbes list of the world's billionaires. Peterffly also topped the Florida billionaires' list in 2016. Forbes said he added $27.6 billion to his fortune.
According to the magazine's annual rich list, Mr Gates' fortune rose $86bn past year to $75bn, followed by investor Warren Buffet, up $14.8bn to $75.6bn.
Tillerson to skip meeting of North Atlantic Treaty Organisation foreign ministers
In Beijing, Tillerson said the US and China should work together to get North Korea to take a "different course". However, some experts argue that stronger actions are not necessary at this time.
As the New York's real estate market has slowed, Forbes began downgrading Trump's net value a year ago, saying in October that his net worth was down to US$3.7b.
Still at number three is Lucio Tan with a $3.7 billion total net worth, $3 million lower than a year ago.
Forbes isn't the only publication tracking Trump's wealth to conclude that he is likely worth much less than he says he is.
The number of USA billionaires on the list was 565, which Forbes attributed to the recent stock market surge since Mr Trump's November 2016 election.
Facebook founder Mark Zuckerberg moved up to number five for the first time, after his fortune rose $11.4 billion in 12 months.
The Asia-Pacific claimed the most billionaires with 720, followed by the US with 565 and Europe with 530.
The US president also would have missed the big stock market rally following his election, "assuming Trump sold off all of his stocks during last year's campaign, as he has claimed", the magazine said.