Year	Percent
1971	61.74269
1972	64.07781
1976	73.16705
1977	75.37369
1978	78.97973
1980	76.6731
1981	77.74605
1982	80.87499
1983	82.01314
1984	82.86415
1988	64.14401
1991	65.63749
1992	61.04488
1993	66.92528
1994	57.48575
1999	37.49731
2002	51.08793
2007	66.05257
2008	71.29241
2009	74.39655
2010	72.51518
2011	76.16053
2012	81.15486
2013	76.83404
2015	69.53687