Year	Percent
1979	79.65475
1980	80.07663
1981	80.3543
1982	80.51081
1983	61.66859
1984	81.17625
1985	81.40808
1986	81.72826
1987	80.85577
1988	81.14502
1989	81.80053
1990	82.66644
1991	83.45675
1992	84.19917
1993	85.01731
1994	85.42763
1995	85.69787
1996	86.08483
1997	86.1769
1998	86.32312
1999	86.35548
2000	86.83007
2001	87.26021
2002	87.55386
2003	87.78018
2005	88.08034
2008	89.10246
2009	89.30579
2010	89.42578
2011	90.19868
2012	90.33167
2013	90.40803
2014	91.89638
2015	90.74496
2016	91.13863
2017	91.20304