The US President has dropped by 222 places on the rankings and now comes in at 766. The number one spot is taken by Amazon boss Jeff Bezos who sits on a fortune of $112billion (£80billion).
This is a huge increase of $39.2billion (£28billion) last year. Second and third place go to Bill Gates and Warren Buffet.
Forbes attribute some of Mr Trump’s loss to the markets, saying that retail real estate in New York “continues to struggle”, however they also believe that Mr Trump’s personality could be having a negative effect on his business.
The President’s golf properties have seen less of a drop in value thanks to market shifts, however, Mr Trump’s hotel licensing and management firm dropped by an estimated $50million (£36million) in the last year.
The Trump brand has downplayed his involvement in business as in Toronto and New York – investors have removed the President’s name from the hotels.
Mr Trump was the first billionaire president in US history when he took office in January 2017.
According to Forbes, the core of Mr Trump’s fortune is tied up in buildings in midtown Manhattan where luxury real estate valies have fallen recently.
He also owns golf courses, a winery and has licensed his name to companies around the world.
Mr Trump’s sons Donald Junior and Eric are running the family business while their father is in office.
Forbes said: “It all adds up to an estimated $3.1bn fortune – a far cry from the $10bn-plus that Trump once claimed but nonetheless enough to make him the richest president in US history.”
Mr Trump was the first US president to attend the World Economic Forum in Davos in 18 years but he was only the sixth richest speaker.
His wealth was outweighed by several Davos regulars.
Microsoft giant Mr Gates attended Davos as did Jack Ma, the founder of Chinese wholesale giant Alibaba, worth $47.2billion (£33.9billion) and Ray Dalio, the investor and hedge fund manager, who is worth $14.1billion (£10billion).
Oliver Williams, head of research at WealthInsight said: “With as many as 12 billionaires set to lecture Davos this year, the average wealth of each of the 433 speakers is skewed into the hundreds of millions.
“The net worth of businessmen such as Bill Gates and Jack Ma dwarfs that of the many journalists, academics and writers, pushing the speakers’ average to over $400m.”