Many firms that sponsor traditional defined benefit pensions have converted their plans to cash balance plans in the last ten years. Cash balance plans combine features of defined benefit (DB) and defined contribution (DC) plans, and yet their introduction has proven considerably more controversial than has the increasing popularity of DC 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 can be viewed largely as a response to better compensate a more mobile labor force. Indeed, many firms appear to increase their pension liabilities through such conversions