Year	Percent
1997	92.0923
1998	91.45785
1999	91.10762
2000	92.29474
2001	92.86535
2002	93.35286
2003	90.83002
2004	88.68693
2005	91.20398
2006	89.97811
2007	88.91167
2008	90.48382
2009	89.50081
2010	89.42288
2011	89.38448
2012	88.50651
2013	88.51744
2014	88.44271
2015	88.87396
2016	88.89525
2017	86.9385