Year	Percent
1975	61.07
1976	61.35
1977	63.78
1978	63.53
1979	60.74
1980	61.65
1981	60.91
1982	61.71
1983	62.41
1984	62.65
1985	62.57
1986	60.57
1987	59.45
1991	62.83