More than 20 percent of the U.S. population—66.7 million Americans—live in homeowners associations, condominium communities and cooperatives according to a new report published by Community Associations Institute (CAI).

The number of associations in the U.S. grew from 10,000 in 1970 and 222,500 in 2000 to 333,600 in 2014, according to the report. CAI estimates that 2015 will end with between 336,000 and 338,000 associations with close to 70 million residents. 

States with the most associations are Florida (47,100), California (43,300), Texas (19,400), Illinois (18,150), North Carolina (13,600), New York (13,400), Massachusetts (12,000), and Georgia and Washington State (10,200 each).

Residents who live in associations are largely satisfied in their communities, according to a 2014 national survey conducted for the Foundation for Community Association Research. The survey found that 90 percent of residents rate their overall community association experience as positive (64 percent) or neutral (26 percent). The remaining 10 percent express dissatisfaction. 

About 2.3 million homeowners serve on community association boards and committees at any one time. These volunteer leaders perform an estimated 78 million hours of volunteer service to their associations annually.

Those living in associations can take advantage of CAI's free online course, An Introduction to Community Association Living, at www.caionline.org/education. The nonprofit organization also offers an online course developed specifically for those who serve on association boards.