Year	Percent
1983	90.76728
1984	90.29134
1985	90.37357
1986	90.33615
1987	90.55807
1988	90.54334
1989	90.21266
1990	90.19865
1991	90.60978
1992	90.12181
1993	89.78652
1994	89.15589
1995	89.01956
1996	88.56186
1997	88.16285
1998	88.01895
1999	88.02354
2000	87.82982
2001	87.90523
2002	87.74034
2003	87.12927
2004	86.32153
2005	86.22021
2006	86.38992
2007	86.6568
2008	86.86771
2009	86.58918
2010	86.55428
2011	86.43522
2012	86.44699
2013	86.85628
2014	87.18117
2015	87.3107
2016	87.77241
2017	88.08008