Megan McCarty Carino

Stock indexes like the Nasdaq or S&P are just lists of top companies, and there are trillions of dollars of investment that just track those lists.

Each index has its own methodology for inclusion, like company profit levels or how many shares are available, says NYU finance professor Aswath Damodaran.

Well, you change the rules.

Several indexes are fast-tracking SpaceX, so it will be included in a matter of days rather than months.

Michael Monahan at Founder ETFs says index funds have to buy stock in proportion to a company's size, no matter the price.

This passive investing has grown bigger than funds managed by investors who research companies and make active bets.

Because SpaceX and the AI companies will likely be selling relatively few public shares at first, the rest are locked up with private investors, competition will be fierce and the price is likely to spike, says Paul Kedrosky, senior fellow at the MIT Initiative on the Digital Economy.

The more the share price rises, the more index funds have to buy, driving the price ever higher and forcing the sale of other stocks to make room.

I'm Megan McCarty Carino for Marketplace.

When the web browser Netscape went public in 1995, it was barely a year old.

That kicked off the dot-com boom, says Jay Ritter, an economist at the University of Florida.

That created a risk for retail investors, but also opportunity to get in on the ground floor of tech companies that would build unimaginable fortunes like Google and Amazon.

Anthropic is only 5, but all have mature businesses generating billions in revenue.

It means gains have accrued to a smaller group of private investors and venture capital firms.

And that important details about these companies' business models have been less transparent, says Minmo Gang, a professor of finance at Cornell.

While these companies have booming revenue, Gang says they're not likely to be profitable in the near future because they're spending so much on hardware.

But there's a lot of pent-up demand to invest in the technology people are increasingly using every day, says analyst Daniel Newman at Futurum Group.

A lot of individual investors have already been trying to scoop up shares ahead of the IPO on the secondary market, not always through official means.

One investment banker offered his Bay Area home for sale in exchange for Anthropic shares.

I'm Megan McCarty Carino for Marketplace.