Over the past 25 years, an important change has occurred in the structure of employer-sponsored retirement plans in the private sector. Although the percentage of the workforce who participate in employer-sponsored retirement plans has remained relatively stable at approximately half of all workers, the type of plan by which most workers are covered has changed from defined benefit (DB) pensions to defined contribution (DC) plans. The responsibilities of managing a DB plan -- making contributions, investing the assets, and paying the benefits to retired workers and their survivors -- lie mainly with the employer. In a typical DC plan, the worker must decide whether to participate in the plan, how much to contribute, how to invest the contributions, and what to do with the money in the plan when he or she changes jobs or retires. As a result of the shift from DB plans to DC plans, workers today bear more responsibility for preparing for their financial security in retirement. According to data collected by the Federal Reserve Board, 45% of households in which the householder or spouse was employed contributed to employer-sponsored retirement plans in 2004, and 58% owned a retirement account of any kind. Among married-couple households in which the householder was under age 35, the median balance in all retirement accounts owned by the household was $19,000 in 2004. Among unmarried householders, the median retirement account balance in 2004 was just $7,000. Among married-couple households headed by individuals between 45 and 54 years old, median retirement assets in 2004 were $103,200.