Year	Percent
1990	69.65
1991	69.54
1992	69.56
1993	69.53
1994	69.48
1995	69.46
1996	69.51
1997	69.56
1998	69.57
1999	69.6
2000	69.7
2001	69.75
2002	69.91
2003	70.02
2004	70.18
2005	70.3
2006	70.47
2007	70.63
2008	70.76
2009	70.86
2010	70.94
2011	71.08
2012	71.22
2013	71.29
2014	71.28
2015	71.06
2016	70.32
2017	69.54
2018	69.44
2019	69.31
2020	68.81