SpaceX joins the Nasdaq 100 less than a month after its Wall Street debut

Less than a month after its initial public offering on Wall Street, SpaceX joined the Nasdaq 100 on Tuesday, a move that added the company’s shares to the portfolios of U.S. retirement funds.

SpaceX has been trading on Wall Street since June 12, and as of Tuesday, it is part of the Nasdaq index, which recently changed its rules.

Large companies can now be added to the index after just 15 days of trading, instead of the three months it used to take. Thus, SpaceX has become the fastest company to be added to a major index following its initial public offering.

Nearly $1.4 trillion is held in index-linked funds. These funds are part of most 401(k) retirement plans, a tax-advantaged investment account that is a pillar of individual savings in the United States.

"Every single one of those funds had to buy SPCX. Not because a portfolio manager made a judgment call... (but) because the index rulebook said so," said Mark Malek of Siebert Financial.