Millions of U.S. workers have little or no savings for retirement, potentially adding to future strains on state and national safety net programs. In addition to federal efforts, a growing number of states have proposed efforts to expand coverage in private sector workplace retirement savings programs. Other countries have also implemented similar efforts. This book examines recent estimates of coverage, including access and participation, as well as characteristics of workers who lack coverage; strategies used by states and other countries to expand coverage; and challenges states could face given existing federal law and regulations.