Elon Musk’s personal fortune jumped by US$36.2bil on Oct 25 after Hertz Global Holdings Inc placed an order for 100,000 Teslas and filings showed a fresh tranche of options in his moonshot pay package vested.

It’s the biggest one-day gain in the history of the Bloomberg Billionaires Index, eclipsing Chinese tycoon Zhong Shanshan’s US$32bil surge last year when his bottled-water company, Nongfu Spring Co, went public. Musk’s net worth of US$288.6bil is now greater than the market value of Exxon Mobil Corp or Nike Inc.

Tesla Inc shares rose 13% on news of the Hertz order, pushing its market value past US$1 trillion . About two-thirds of Musk’s net worth is tied directly to shares and options in the electric-car company, of which he is co-founder and chief executive officer.

Musk is increasingly pulling away from his fellow mega-billionaires when it comes to the size of his fortune. Amazon.com Inc’s Jeff Bezos ranks second with US$192.6bil , according to the Bloomberg index.

Musk’s extraordinary jump in wealth comes as Democratic lawmakers, with US President Joe Biden’s support, draw up a plan to tax unrealised gains of the very richest Americans. Senate Finance Committee Chair Ron Wyden, an Oregon Democrat, is laying out the so-called billionaires’ income tax, which would be aimed at those with US$1bil in assets, or three consecutive years of US$100mil or more in income.

The stock-based nature of Musk’s fortune has made it possible for him to gain billions of dollars in paper wealth and become the world’s richest person while having few liquid assets. He accepts no salary from Tesla and part of his stake is pledged as collateral for personal loans, according to company filings. He told a federal jury in 2019 that despite his multibillionaire status, he didn’t have much cash. Last year he announced on Twitter he planned to sell his homes and “almost all” his physical possessions.

Even before the Hertz deal, Tesla shares have climbed in recent weeks. The auto maker’s stock price is up 45% this year, more than double the gain of the S&P 500 Index, as investors continue to reward green technologies.

A surge in Tesla stock isn’t the only source of wealth gains for Musk. The seventh tranche of Musk’s massive 2018 stock option package vested in the third quarter, according to a regulatory filing Monday, adding about US$8bil to his net worth.

 - Bloomberg