Go to U.S. Bureau of Labor Statistics - Collective Bargaining and Union Membership.

Visit the U.S. Census Bureau's Statistical Abstracts Series (historical data through 2012) and navigate to the Labor Force, Employment, and Earnings section.

The Union Membership, Coverage, and Earnings from the CPS, constructed and maintained by Barry Hirsch (Georgia State University) and David Macpherson (Trinity University), includes public and private sector labor union membership, coverage, and density estimates compiled from the monthly Current Population Survey using Bureau of Labor Statistics methods.

See the U.S. Department of Labor - Office of Labor-Management Standards (OLMS) for private and public sector agreements.

University of California, Berkeley maintains a comprehensive Labor Contracts Database.

For collective bargaining agreements in certain sports, see:

• National Hockey League Players' Association
• Major League Baseball Players Association