Automatic Data Processing Inc. (NASDAQ: ADP)

ADP processes payroll for about 1 in 6 U.S. workers — roughly 41 million people every pay period. It's the largest payroll and human capital management company in the world, with about $19 billion in annual revenue. Beyond payroll, ADP provides HR outsourcing, benefits administration, tax filing, and workforce management. The company's monthly jobs report (ADP National Employment Report) is a closely watched economic indicator.

Two segments: Employer Services (payroll, HR, tax — ~65% of revenue) and Professional Employer Organization (PEO) Services (~35% — where ADP becomes the co-employer and handles all HR functions). The float on client payroll funds generates significant interest income. Revenue is highly recurring — once a company sets up payroll with ADP, switching costs are enormous.

Henry Taub founded Automatic Payrolls, Inc. in 1949 in Paterson, New Jersey, processing payroll manually. The company went public in 1961 and has increased its dividend for 49 consecutive years. ADP spun off its brokerage services division as Broadridge Financial Solutions in 2007. The company successfully fought off an activist campaign by Bill Ackman's Pershing Square in 2017.