Over the last 25 years, pension coverage has shifted primarily from "traditional" defined benefit (DB) plans, in which workers accrue benefits based on years of service and earnings, toward defined contribution (DC) plans, in which participants accumulate retirement balances in individual accounts. DC plans provide greater portability of benefits, but shift the responsibility of saving for retirement from employers to employees. This book addresses the following issues: (1) What percentage of workers participate in DC plans, and how much have they saved in them? (2) How much are workers likely to have saved in DC plans over their careers and to what degree do key individual decisions and plan features affect plan saving? (3) What options have been recently proposed to increase DC plan coverage, participation, and savings? GAO analysed data from the Federal Reserve Board's 2004 Survey of Consumer Finances (SCF), the latest available, utilised a computer simulation model to project DC plan balances at retirement, reviewed academic studies, and interviewed experts. This is an excerpted and indexed version.