A computer system having a processor and a data storage device for processing data related to an annuity product, the annuity product having a contract value and an interest rate. The processor is configured to determine an amount of interest for crediting to the contract value based on the contract value and the value of the interest rate; determine a difference between the current value of an index independent of the value of any financial instrument and the prior period value of the index; based on the determined difference between the current value of the index and the prior period value of the index, determine a value of an additional amount for crediting to the contract value; and, based on the contract value, the amount of interest for crediting and the value of the additional amount for crediting, determine an updated contract value.