By not fast-tracking SpaceX's inclusion, the S&P 500 withholds a crucial "wall of automatic demand" from passive index funds. This means when insider shares unlock, SpaceX must rely on active investors to buy them, potentially creating significant price volatility that would have otherwise been absorbed by passive inflows.

A key flaw in pure indexing is the forced, predictable trading around index rebalancing. When a stock is added, all index funds must buy it, often at an inflated price due to front-running. David Booth estimates this systematic inefficiency costs index fund investors a "run up" of about 4% on new additions.

For companies like SpaceX, Nasdaq now allows index inclusion in just 15 days (down from six months) and artificially inflates weight by treating a 5% float as 15%. This creates a massive, predictable, and forced buying event from index funds, which must sell other holdings to accommodate the new stock, distorting the market.

Index providers are no longer neutral. By changing inclusion rules to quickly add "hot" IPOs like SpaceX, they are making active bets on specific companies. This blurs the line between active and passive investing, requiring investors to have an opinion on the index's strategy itself rather than just blindly buying.

Many stocks added to the S&P 500 are later removed. Index investors are forced to buy these "flip-flop" stocks *after* they have already appreciated significantly (avg. +75%), only to then participate fully in their subsequent decline (avg. -70%), locking in a substantial loss.

Stocks that are added to an index and later removed (a "flip-flop") systematically damage returns. The index buys after a 75% run-up but sells after a 70% drop. Because the index investor missed the initial gain but participates fully in the loss, the net effect is a significant performance drag.

Many assume the S&P 500 is a purely rules-based, passive index. In reality, a committee makes discretionary decisions on inclusions and exclusions. For example, MicroStrategy met the technical criteria for inclusion but was denied by the committee.

So-called passive indexes have a small but impactful "active side" in their turnover. This component behaves like a flawed momentum strategy, forcing the index to systematically buy stocks after they've surged and sell them after they've plummeted, creating a performance drag.

Index providers are including massive IPOs like SpaceX into benchmarks within days of listing. This forces passive index funds, which hold vast amounts of retirement savings, to automatically buy these shares while they are still highly volatile, exposing everyday savers to the risk of buying at an improper price.