The University of Michigan Survey Research Center has conducted the SCA on a regular
basis for over 50 years. For three decades, beginning in the late 1940s, it was conducted as
an area probability in-person survey. Steeh (1981) drew on SCA results from 1954 through
1976 to describe the nature of the substantial response rate declines during that period
In 1977, the SCA was converted to a random digit dial telephone survey, which has now
been repeated every month for more than a quarter of a century.