Elon Musk is having a better 2020 than most people.

Tesla‘s CEO passed Microsoft co-founder Bill Gates last week to become the world’s second-richest person, according to the Bloomberg Billionaires Index. Musk started the year as the 35th richest, and his net worth has more than quadrupled since then, thanks mostly to Tesla’s soaring share price.

Tesla’s market cap topped $500 billion for the first time last week, increasing Musk’s wealth to about $128 billion. About three-quarters of his net worth is based on Tesla’s shares, which surged further after recent news that the company would join the S&P 500 index in December.

Gates and Musk have had several public spats over electric vehicles and COVID-19. Gates’ charitable foundation has helped fund research to develop a vaccine for the coronavirus, while Musk insisted in the spring that the disease was not a major concern.

It’s only the second time since Bloomberg started ranking billionaires eight years ago that Gates didn’t hold one of the top two spots. Musk still trails Amazon founder Jeff Bezos.