Year	Percent
1991	71.27
1992	71.08
1993	70.84
1994	70.63
1995	70.44
1996	70.25
1997	70.15
1998	70.04
1999	69.94
2000	68.96
2001	67.92
2002	66.78
2003	65.61
2004	64.44
2005	63.26
2006	64.46
2007	65.65
2008	66.79
2009	67.71
2010	68.62
2011	69.48
2012	70.25
2013	70.95
2014	71.65
2015	72.31
2016	72.96
2017	72.76
2018	72.54
2019	72.31
2020	69.75