In 1970, according to the American Housing Survey (from HUD and the Department of Commerce ,then called the Annual Housing Survey, Table A-1, p. 32), 36% of the 67 million households in America had air conditioning, 11% had central air. This is the earliest data available from this survey.
In 2005, the most recent data from the same survey, (Table 2-4, p. 66) 82% of the 15 million households with income below the poverty line had air conditioning, 52% had central air.
