Year	Percent
1990	81.68
1991	81.53
1992	81.7
1993	81.88
1994	82.05
1995	82.23
1996	82.4
1997	82.58
1998	82.75
1999	82.93
2000	83.1
2001	83.27
2002	83.44
2003	83.61
2004	83.77
2005	83.92
2006	84.07
2007	84.22
2008	84.35
2009	84.49
2010	84.61
2011	84.74
2012	84.86
2013	84.94
2014	84.99
2015	85.05
2016	85.15
2017	85.27
2018	85.36
2019	85.46