The S&P 500 index, where trillions in retirement savings are invested, said no to the SpaceX IPO, the biggest in history. Here's what that means for portfolios.

Two big stock indexes changed their rules recently in a way that will fast-track Elon Musk's company for inclusion.

SpaceX IPO is showing investors that passive investing is not fully automatic. Index funds follow rules set by people, and those rules can change.