Year	Percent
1992	87.04968
1993	87.38367
1994	87.11223
1995	87.45729
1996	87.5543
1997	87.68646
1998	87.9167
1999	88.14227
2000	88.82304
2001	89.40704
2002	89.52033
2003	88.9447
2004	88.92106
2005	88.81128
2006	88.32225
2007	88.17813
2008	88.48429
2009	87.92859
2010	87.12965
2011	87.0117
2012	87.17115
2013	87.59052
2014	87.13762
2015	87.11924
2016	86.9562
2017	87.32363