A method and system of providing comparative cost information for health insurance plans. Claims files are generated for the reference population of real historical patients for each the plans. Information is presented to users on the distribution of out-of-pocket costs for health care that users are likely to incur in the coming year, based on the parameters of health plans, information on the user and his/her household, and the actual health care use and costs for a reference population comparable to the users. Information is presented to users on optimal contributions to their flexible spending account for health care in the coming year and solving a dynamic numerical model based on users' objective function; solutions are based on the parameters of health plans, information on the user and his/her household, and the actual health care use and costs for a reference population comparable to the user.