Today's decline came amid a global equity sell off that has wiped out US$93b ($128b) from the world's 400 biggest fortunes since Saturday.
The billionaires shed US$37.3b today as stocks and bonds both slumped, and oil sank after the International Energy Agency's prediction that a glut will extend into next year.
The world's second-richest person, Inditex founder Amancio Ortega, leads the 400 richest people with a decline of US$3.3b since the sell off began, according to the index.
Microsoft co-founder Bill Gates, the world's richest person with US$87.3b, has lost US$2.4b. Amazon.com founder Jeff Bezos, the world's third-richest person with $66.2b, has shed US$1.9b.
Buffett, who's fortune is mostly in Berkshire shares, has lost US$1.6b in total in the sell off.
New Zealand's richest person Graeme Hart comes in at number 168 on the index at US$7.4b.
Wells Fargo was overtaken by JPMorgan Chase & Co as the world's most valuable bank today.
It has fallen 5.9 per cent since Friday, when the Consumer Financial Protection Bureau announced fines stemming from the fake accounts. The drop since then compares with a 2.5 per cent fall for the Standard & Poor's 500 Index.