Year	Percent
1970	18.37
1971	18.37
1972	18.37
1973	18.37
1974	18.37
1975	18.37
1976	18.36
1977	18.36
1978	18.38
1979	18.38
1980	24.41
1981	25.23
1982	23.03
1983	23.01
1988	22.16
1990	22.83
2003	39.16