(Bloomberg) -- Shares of Tesla Inc., Elon Musk’s public company, have been in freefall for the last few months. But shares in his private companies aren’t.

Secondary market investors have sent the collective valuation of four of Musk’s private entities up 45% since the US election, according to a new analysis from trading platform Caplight, exclusively shared with Bloomberg.

Caplight aggregated secondary transaction data along with other signals, such as buyer interest, to estimate a daily share price for Musk’s SpaceX, Neuralink Corp., the Boring Company and xAI. Musk’s artificial intelligence lab, built to rival OpenAI, has driven most of the gains in this portfolio, according to Caplight. The firm’s data shows the xAI share price increased 110% since Nov. 5.

Recent xAI deal talks with investors suggest a valuation of $75 billion for the startup. Caplight estimated that, as of March 10, xAI traded in secondary markets at a value of $96 billion. The trading platform offers buyers access to these four Musk companies and Tesla in an “Elon Musk Crossover Index.”

Caplight excluded Musk’s X from its analysis because the social media platform has “very limited” secondary market activity, according to Javier Avalos, Caplight’s chief executive officer.

Secondary transactions allow outside investors to buy into private companies, often after early employees or backers offload shares. They’re becoming increasingly common in Silicon Valley as the largest venture-backed startups, such as SpaceX, hold off on public listings.

Since secondary investors have scant access to financial figures, these share estimates are a better indicator of investor enthusiasm than business performance. Within Musk’s empire, SpaceX, in particular, attracts investors “willing to pay a premium to the company’s latest tender offer price,” Avalos said.

In Augment, another secondary trading platform, account holders could see that shares of SpaceX and xAI have more than doubled since the election, as of March 12.

Not every company is hot. The Boring Company, Musk’s tunneling enterprise, saw a decline of 7.8% in its value since the US election.

Even without secondary markets, Musk has had little trouble drumming up investor interest in X. After stretches of advertiser withdrawals and financial tumult at X, including steep writedowns by Fidelity Investments, Bloomberg reported in February that the social network was in talks to raise additional funding for a valuation of $44 billion, the same price Musk paid in 2022 when it was called Twitter.

After Donald Trump’s election, investors pumped up the price for Tesla, convinced Musk’s relationship and administration role would boost the automaker’s fortunes. But production difficulties and a backlash to Musk’s job-cutting crusade at the Department of Government Efficiency (DOGE) have erased Tesla’s post-election gains.

In private markets, Musk can be selective about the investors who access his companies. A larger number of investors are able to gain exposure through special purpose vehicles, or SPVs. The mechanism allows investors to sell their access to other would-be backers — pooling capital from a number of sources.

According to Caplight, SPVs represented 12% of the total secondary transaction volume the firm measured at the start of 2023. They accounted for 43% of the volume by the final quarter of 2024.

--With assistance from Katie Roof.