If you have a 401(k), how much SpaceX stock will you own?

It’s common for companies to start with a smaller amount of tradable stock, but SpaceX’s stock volume is particularly small. It may be a strategic play to raise prices by limiting inventory availability, said David Brown, associate professor of finance at the University of Arizona.

When it comes to maneuvering for successful IPOs, “companies are much better suited today than they were a few decades ago,” he said.

As restrictions on insiders like Mr. Musk or SpaceX employees expire, more shares will be available for trading. If the stock price is stable or climbs higher, more public movement could mean more exposure to SpaceX in index funds.

SpaceX is set for a small fraction of most people’s investment for now.

“IPOs are not moving retirement portfolios meaningfully right away,” Rodney Comegys, Vanguard Capital Management’s chief investment officer and head of global equity at Vanguard, said in a statement. “Even mega IPOs enter broad indexes with very small weights, so the short-term impact on 401(k)s is limited.”

The sheer size of these new public companies should cause index funds to think hard about the best time to list them, Professor Brown said. (Artificial intelligence companies Anthropic and OpenAI have also begun preparing for IPOs.) “For most investors, that’s what it’s going to hit,” he said.

About data

SpaceX’s ownership estimates use each index’s float-adjusted weighting rules, assuming its publicly traded stock is worth roughly $150 per share based on its opening price.

To estimate ownership through index funds, we calculate a weight for each company based on the company’s volatility-adjusted capitalization and the total market capitalization the index tracks. Total US market capitalization, market capitalization for the S&P 500, and weights for use of the Vanguard VTI and Invesco QQQ index funds were provided by Morningstar. The total market share of the Nasdaq 100 is calculated from its index page as of May 29. Weights and market capitalization change daily.