Year	Percent
1990	63.82
1991	64.02
1992	64.33
1993	65.12
1994	66.29
1995	67.23
1996	67.03
1997	66.9
1998	66.88
1999	67.25
2000	67.4
2001	67.17
2002	67.09
2003	66.62
2004	66.71
2005	66.95
2006	66.62
2007	66.62
2008	67.07
2009	68.26
2010	69.31
2011	69.87
2012	70.46
2013	71.22
2014	71.93
2015	72.56
2016	72.76
2017	73.32
2018	73.51
2019	73.6
2020	71.14