https://www.spglobal.com/spdji/en/documents/research/research-what-happened-to-the-index-effect.pdf
The S&P 500 had 715 additions and 711 deletions between January 1995 and June 2021, averaging around 27 constituent adds and drops per year 投資指數或者大盤的好處就是不需要擔心你選擇的TOP 10在10年後會不會連TOP 100都進不了，指數自動幫你take care好了，self cleansing
