Year	Percent
1983	92.12513
1984	91.81916
1985	91.79266
1986	92.55319
1987	91.76107
1988	91.86653
1989	92.00415
1990	91.91102
1991	92.07136
1992	91.67269
1993	90.65255
1994	91.55182
1995	90.76571
1996	90.94163
1997	91.82267
1998	91.14183
1999	92.08133
2000	91.26247
2001	92.99141
2002	92.1083
2003	93.52384
2004	92.23248
2005	92.73814
2006	92.6317
2007	93.32666
2008	94.85653
2009	91.10243
2010	91.61894
2011	91.47838
2012	91.70197
2013	91.41254
2014	91.19898
2015	89.89327
2016	89.44839
2017	89.87229