Year	Percent
1990	83.66
1991	83.54
1992	83.79
1993	83.58
1994	83.57
1995	83.69
1996	84.01
1997	84.33
1998	84.21
1999	84.3
2000	84.23
2001	83.89
2002	83.5
2003	83.14
2004	82.88
2005	82.89
2006	83.04
2007	83.13
2008	83.19
2009	82.71
2010	82.25
2011	81.69
2012	81.6
2013	81.17
2014	81.09
2015	81.02
2016	81.46
2017	81.83
2018	82.18
2019	82.62