Year	Percent
1990	84.66
1991	84.68
1992	84.66
1993	84.61
1994	84.47
1995	84.34
1996	84.2
1997	84.05
1998	83.86
1999	83.64
2000	83.39
2001	83.18
2002	82.93
2003	82.65
2004	82.34
2005	82.03
2006	81.81
2007	81.6
2008	81.4
2009	81.24
2010	81.13
2011	81.14
2012	81.19
2013	81.24
2014	81.3
2015	81.35
2016	81.34
2017	81.33
2018	81.34
2019	81.38