Year	Percent
1987	90.57692
1988	91.91321
1989	92.2179
1990	92.36641
1991	91.39785
1992	91.86176
1993	91.76194
1994	90.86431
1995	92.23031
1996	93.30835
1997	92.958
1998	94.36514
1999	92.41255
2000	93.78774
2001	94.65069
2002	95.31428
2003	94.17228
2004	94.41336
2005	93.7601
2006	94.50469
2007	94.83871
2008	94.40449
2009	93.77247
2010	93.61922
2011	93.17293
2012	92.44321
2013	92.44947
2014	93.14409
2015	91.21059
2016	91.30973
2017	91.28403