Year	Percent
1990	83.04
1991	82.85
1992	82.95
1993	83.02
1994	83.01
1995	82.91
1996	82.76
1997	82.53
1998	82.27
1999	82.02
2000	81.81
2001	81.58
2002	80.39
2003	79.7
2004	81.21
2005	81.15
2006	80.65
2007	81.66
2008	81.95
2009	81.24
2010	80.84
2011	80.67
2012	80.95
2013	80.78
2014	84.06
2015	84.46
2016	81.93
2017	83.27
2018	83.28
2019	83.51