Computer-implemented methods of creating and maintaining stock indexes are provided. For a stock index of a particular size, a band is defined around the upper and/or lower limits of the stock index. To be added to, or dropped from, a particular stock index, the stocks must fall outside of the bands for that particular stock index size. Stock migration is controlled using a systematic stock migration process so that stocks are gradually added and deleted from an index. Stock investment style is determined in a multi-dimensional process, instead of a linear process. Furthermore, the number of stocks in the stock index need not be a fixed value, but may depend upon how many stocks meet predefined criteria at any given point in time.