Elon Musk was the second person ever to amass a personal fortune of more than $US200 billion ($293 billion), breaching that threshold in January 2021, months after Jeff Bezos.

The Tesla chief executive officer has now achieved a first of his own: becoming the only person in history to erase $US200 billion from their net worth.

Musk, 51, has seen his wealth plummet to $US137 billion ($201 billion) after Tesla shares tumbled recently, including an 11 per cent drop last Tuesday, according to the Bloomberg Billionaires Index.

His fortune peaked at $340 billion ($499 billion) on November 4, 2021, and he remained the world’s richest person until he was overtaken this month by Bernard Arnault, the French tycoon behind luxury-goods powerhouse LVMH.

The round-number milestone reflects just how high Musk soared during the run-up in asset prices during the easy-money pandemic era. Tesla exceeded a $1 trillion market capitalisation for the first time in October 2021, joining the likes of ubiquitous technology companies Apple, Microsoft, Amazon.com and Google parent Alphabet, even though its electric vehicles represented only a sliver of the overall auto market.

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Now Tesla’s dominance in electric cars, the foundation of its lofty valuation, is in jeopardy as competitors catch up. It’s offering US consumers a rare $7,500 discount to take delivery of its two highest-volume models before year-end, while also reportedly reducing production at its Shanghai plant.

Meanwhile, with pressure on Tesla intensifying, Musk has been preoccupied with Twitter, which he acquired for $44 billion in late October. He’s applied a move-fast-and-break-things approach such as firing staff then asking them to come back and applying content policies haphazardly to justify banning the accounts of some prominent journalists who cover him.

The decline in Tesla shares has been so steep — the shares fell 65 per cent in 2022 — and Musk has sold so much this year to help cover his Twitter purchase, that they’re no longer his biggest asset, according to Bloomberg’s wealth index.