Year	Percent
1971	40.54577
1972	39.68444
1973	42.74565
1974	43.53714
1975	51.38125
1976	51.73237
1977	64.95142
1978	66.17605
1980	73.24264
1983	56.71656
1985	65.13601
1986	63.99333
1987	58.13206
1988	60.90285
1989	59.21727
1993	59.3705
1999	56.99791
2000	55.99988
2004	79.60338
2007	66.65158