Year	Percent
1998	92.89534
1999	92.18194
2000	91.78458
2001	91.26205
2002	91.32593
2003	90.00537
2004	87.63993
2005	87.05915
2006	87.10314
2007	86.78646
2008	86.22791
2009	84.42546
2010	84.14591
2011	84.32376
2012	84.58882
2013	84.50821
2014	84.84414
2015	85.09964
2016	84.70689
2017	84.94535