A computer system (10) including a processor (12) and a storage device storing a computer program product for rebalancing a capitalization weighted stock index are described. The computer program includes instructions for causing a computer to classify stocks in the index as Large Individual Stock if a stock has a capitalization weight above or equal to a first threshold or as a Small Individual Stock if the stock has a capitalization weight below the first threshold. The computer program causes the computer to scale down the Large Individual Stocks by an excess capitalization weight of the large stocks and distribute an aggregated excess capitalization weight of the Large Individual Stocks over the capitalization weights of the Small Individual Stocks. An iterative redistribution of excess capitalization over all Small Individual Stocks can be used to provided for less than proportional distribution of excess capitalization to very small capitalized stocks. The index rebalancing software (40) retains a capitalization weighting characteristic while permitting the index to conform to generally accepted accounting, economic and tax standards. Index rebalancing is accomplished while maintaining the original relative position of stocks and reducing the market impact of rebalancing on the Small Individual Stock group.