I recently read a paper from Jeremy Siegel and Jeremy Schwartz titled “The Long-term Returns on the Original S&P 500 Firms”.

In this paper the authors calculate the total returns of a buy and hold of the original 500 companies in 1957. They found that on average 20 stocks annually have been added and deleted from the index (without considering that a merger of two S&P 500 companies is an addition to the index) since 1957. The authors also used three methods of calculating the returns: