Year	Percent
1971	20.27032
1972	42.31094
1973	45.04691
1974	59.03731
1975	80.91063
1976	77.55664
1977	88.10664
1978	88.26191
1979	83.83331
1980	78.82155
1981	82.52573
1983	88.00192