Indexes are not funds, correct. However, the SP500 index is one of the few indices that is strongly represented in 401K plan options. That changes its role fr

Indexes are not funds, correct. However, the SP500 index is one of the few indices that is strongly represented in 401K plan options. That changes its role from "communicate some metric about the market" to forced buying of the metric. which makes changing the metric, especially in such a drastic way, consequential.