Starting February, investors in equity mutual fund schemes could see a shrinkage in performance of at least some of their investments vis-a-vis the indices they are benchmarked against.The Securities and Exchange Board of India (Sebi) has asked all mutual funds to disclose performance of their schemes based on total return variant of an index (TRI). At present, most of the mutual fund schemes are benchmarked to the price return variant of an index(PRI).