Table 1. Rates of Participation in ACOs Among 67 891 Physician Groups Nationally, 2012-2014.

Characteristic	Physician Groups, No. (%)
ACO participation (2012-2014)	7215 (10.6)
Began participating
2012	3038 (4.5)
2013	2255 (3.3)
2014	1922 (2.8)

Abbreviation: ACO, accountable care organization.