Year	Percent
1990	83.99
1991	83.82
1992	83.75
1993	83.56
1994	83.43
1995	83.29
1996	83.16
1997	83.24
1998	83.26
1999	83.75
2000	83.98
2001	83.73
2002	83.85
2003	83.91
2004	83.8
2005	84.14
2006	84.57
2007	84.52
2008	84.87
2009	85.07
2010	84.95
2011	85.3
2012	85.56
2013	85.71
2014	86.02
2015	85.84
2016	86.1
2017	86.56
2018	86.89
2019	87.22