US President Donald Trump has tumbled down more than 200 places in the world's billionaire rankings after losing around $400 million in his net worth from last year. The business tycoon, with $3.1 billion is now ranked 766th this year, down from a 544th ranking last year. Forbes, the American magazine which compiles a list of the world's richest people annually, attributed his decline to "a tough New York real estate market, particularly for retail locations; a costly lawsuit and an expensive presidential campaign." Trump also lost out around a billion dollars in net worth in 2017.