Year	Percent
1990	72.78
1991	73.05
1992	73.5
1993	74.19
1994	74.69
1995	75.13
1996	74.68
1997	74.55
1998	74.8
1999	75.33
2000	75.96
2001	75.46
2002	75.49
2003	76.05
2004	77.13
2005	78.56
2006	78.97
2007	80.04
2008	81.39
2009	82.71
2010	83.78
2011	83.57
2012	83.25
2013	82.97
2014	82.87
2015	83.01
2016	82.51
2017	82.31
2018	82.11
2019	82.02
2020	80.95