Year	Percent
1980	49.39062
1981	60.11272
1982	57.07213
1983	53.14461
1984	53.76186
1985	61.55007
1986	63.06619
1987	56.08604
1988	71.16288
1989	57.98154
1990	50.36905
1991	58.38929
1992	76.15801
1993	65.89028
1994	58.34531
1995	70.94458
1996	72.05593
1997	69.67889
1998	64.19863
1999	71.11564
2000	63.34847
2001	62.34771
2002	57.58215
2003	61.39067
2004	84.53326
2005	78.70513
2006	92.89559
2007	100.3627
2008	84.61087
2009	81.06324
2010	94.30085
2011	94.38918
2012	83.70974
2013	80.78128
2014	77.90901
2015	78.16983
2016	69.01985
2017	63.29988