1936 ACNielsen begins radio market measurement with nationwide sample of 800 homes.
1950s The radio measurement model migrates to TV.
1963 ACNielsen begins measurement system for sales at mass retail outlets.
1979 ACNielsen begins using scanner data to track retail sales.
1984 Dun & Bradstreet acquires ACNielsen, culminating 15 years of off-and-on talks and wedding D&B's database prowess with ACNielsen's data.
1996 D&B divests ACNielsen as stand-alone publicly traded company.
1997 D&B divests Nielsen Media Research as part of Cognizant Corp., also including IMS Health.
1998 ACNielsen acquires BASES simulated market-testing system.
1999 ACNielsen forms Nielsen/NetRatings.
2000 VNU acquires Nielsen Media Research.
2001 VNU acquires ACNielsen.
2005 VNU proposes to acquire IMS Health. Shareholders balk, leading CEO Rob van den Bergh to resign and board to seek sale to private-equity consortium.
2006 Valcon Acquisition consortium completes purchase of VNU.