Year	Percent
1990	73.46
1991	73.31
1992	73.15
1993	72.96
1994	72.76
1995	72.56
1996	72.37
1997	72.25
1998	72.15
1999	72.06
2000	71.04
2001	69.96
2002	68.8
2003	67.6
2004	66.37
2005	65.12
2006	66.29
2007	67.47
2008	68.61
2009	69.68
2010	70.64
2011	71.52
2012	72.32
2013	73.04
2014	73.73
2015	74.39
2016	75.03
2017	74.78
2018	74.5
2019	74.24
2020	71.89