year whitep blackp
1972 57.4 28.8
1973 63.6 35.8
1974 66.3 36.3
1975 63.2 31.9
1976 67.5 41.1
1977 70 41.6
1978 69.4 43
1980 70.3 39.1
1982 76.9 48.4
1983 76.2 45
1984 74.5 43.5
1985 79 49.7
1986 75.3 42.7
1987 73.7 42.9
1988 76 42.5
1989 76.5 56.1
1990 77.7 52.3
1991 71.4 42.7
1993 75.4 51.5
1994 78.3 50.7
1996 75.5 50.3