Professor Jeffrey Wurgler's research on index funds is referenced
— June 13, 2016
Excerpt from Kiplinger -- "Indexes are constructed and then left alone for the most part, right? Not really. Even the S&P 500, which is weighted by market value and is not rebalanced, undergoes 20 to 25 changes in an average year as companies are added to and removed from the index, according to a study by Jeffrey Wurgler, a professor at NYU Stern School of Business."