Year	Percent
1990	69.01244
1991	68.97921
1992	68.06015
1993	69.70765
1994	69.76817
1995	70.28507
1996	71.19816
1997	72.27298
1998	72.38118
1999	71.41558
2006	74.78395
2007	76.45178
2009	75.12821
2010	76.76036
2011	77.96464
2012	79.12622
2013	80.12622
2014	81.03062
2015	81.53431
2016	81.42865
2017	80.92518