A set of indices is provided which allows accurate tracking of interest rate swap (IRS) markets. The indices are calculated using market data and synthetic purchasing and selling of synthetic interest rate swaps utilizing the present market data. The value of the synthetic interest rate swaps are the basis for the value of a particular index. The purchasing and selling of the synthetic interest rate swap occurs at a frequency to minimize effects of shortening terms on the index. One subset of the IRS indices reflects a plain-vanilla swap for a specific term of years. Another subset of the IRS indices reflects a spread between two specific terms of years. A third subset of the IRS indices reflect two spreads, sometimes referred to as a butterfly, between a middle term of years and a shorter term of years and the same middle term of years and a longer term of years.