Year	Percent
1990	80.88
1991	81.16
1992	81.28
1993	81.22
1994	81.22
1995	81.29
1996	81.15
1997	81.25
1998	81.48
1999	81.75
2000	82.01
2001	82.4
2002	82.72
2003	82.95
2004	83.19
2005	83.44
2006	83.64
2007	83.83
2008	83.96
2009	83.96
2010	84.05
2011	83.91
2012	83.63
2013	83.52
2014	83.5
2015	83.5
2016	83.54
2017	83.52
2018	83.55
2019	83.57