While Americans might want to ignore all the hubbub around SpaceX, Elon Musk and initial public offerings (IPOs), their 401(k) pension accounts likely can't.

SpaceX is now worth US$2.1 trillion after its stock launched 19.2 per cent higher in its debut on Wall Street. Whether or not you believe it deserves to be worth more than Exxon Mobil, Bank of America and Coca-Cola combined, the collective market does. And if SpaceX maintains that big a value, it will join some high-profile stock indexes.

Many of these indexes don't care about how realistic a company's growth plans are or who its CEO is. They're simply trying to show how slices of the market, or the whole thing, are performing. And if SpaceX is big enough to meet the qualifications to join those indexes, whether it's in a few weeks or a year, it will gain entry.