Year	Percent
1990	69.92
1991	70.01
1992	70.03
1993	70.05
1994	70.08
1995	70.12
1996	70.14
1997	70.16
1998	70.19
1999	70.22
2000	70.27
2001	70.33
2002	70.39
2003	70.46
2004	70.53
2005	70.59
2006	70.68
2007	70.75
2008	70.83
2009	70.9
2010	70.98
2011	71.06
2012	71.15
2013	71.06
2014	70.94
2015	70.81
2016	70.65
2017	70.49
2018	70.27
2019	70.04
2020	66.88