Насколько быстро меняется состав американских фондовых индексов?

ну и там ещё коэффициент — в их терминологии «divisor»

//The divisor, currently approximately 8.3 billion,^[35] is a number that is adjusted to keep the value of the index consistent despite corporate actions that affect market capitalization and would otherwise affect the calculation formula, such as additional share issuance, share buybacks, special dividends, constituent changes, rights offerings, and corporate spin-offs. Stock splits do not affect the divisor since they do not affect market capitalization.^[3] When a company is dropped and replaced by another with a different market capitalization, the divisor needs to be adjusted in such a way that the value of the S&P 500 index remains constant. All divisor adjustments are made after the close of trading and after the calculation of the closing value of the S&P 500 index.// *

— это всё к вопросу о том, можно ли «купить SP500», и что это будет практически (экономически, финансово) означать...

Интересно, кстати, как этот «divisor» менялся исторически ...
______________________
* = https://en.wikipedia.org/wiki/S%26P_500_Index