Index rules decide where trillions in retirement money goes, and a rule change means your savings may soon own private giants like SpaceX and OpenAI whether you want it or not.

• The Nasdaq-100 tracks the biggest tech names, and funds that follow it must buy any stock added to the list.
• That forced buying creates billions in automatic demand, so joining the index is close to a money printer for a company.
• The firms that set and follow these rules effectively steer where everyone's money flows.
• The entry rules changed on May 1, opening the door for names like SpaceX, OpenAI, and Anthropic to land in ordinary 401(k)s.

Outlook: Expect more private tech giants to find their way into index funds, putting them in retirement accounts by default rather than by choice.