Many firms that sponsor traditional defined benefit pensions have converted these plans to cash balance plans in the last en years. Cash balance plans in the last ten years combine features of defined benefit and defined contribution plans, and yet their introduction has proven considerably more controversial than has the increasing popularity of defined contribution plans. The goal of this study is to estimate a hierarchy of the influences on the decision of a firm to convert its traditional defined benefit pension plan to a cash balance plan. Our results indicate that cash balance conversions have been undertaken in competitive industries with tight labor markets and thus can be viewed at least in part as a response to better compensate a more mobile labor force. Indeed, many firms appear to increase their pension liabilities through such conversions.