Year	Percent
1979	84.07602
1980	84.41935
1981	84.50974
1982	84.91762
1983	85.24898
1984	85.31056
1985	85.36133
1986	85.55249
1987	84.40061
1988	84.58097
1989	84.93111
1990	85.45141
1991	86.02817
1992	86.59622
1993	87.06303
1994	87.26973
1995	87.43484
1996	87.55798
1997	87.43922
1998	87.63617
1999	87.52057
2000	87.73715
2001	87.94346
2002	88.03251
2003	88.11937
2005	88.11798
2008	88.68135
2009	88.82873
2010	88.77113
2011	89.67001
2012	89.73768
2013	89.7606
2014	91.07351
2015	89.86215
2016	90.23136
2017	90.26874