Comment by stubish

This seems a sensible thing to do. If you change the rules on how things end up on your index, you force everyone using that index to reevaluate it. Your index is now perceived as more volatile (and probably is), and all the finance people need to reevaluate the risk of their index funds and decide if it is now 'growth', 'high growth' or whatever bucket it belongs in based on the new risk profile. And then all the portfolios need to be rebalanced. Which all takes time, more time than was being proposed. The sensible thing to do is to create a new index with the new rules.