aFor the General Social Survey, the 1970–74 period includes data from 1972 and 1974; the 1975–79 period includes data from 1975, 1976, 1977, and 1978; the 1980–84 period includes data from 1982 and 1983; the 1985–89 period includes data from 1985, 1986, 1988, and 1989; and the 1990–94 period includes data from 1990, 1991, 1993, and 1994. For the Current Population Survey, the 1980–84 period includes data from 1980 only; the 1985–89 period includes data from 1985 only; and the 1990–94 period includes data from 1990 only.