Year	Percent
1990	75.4
1991	75.44
1992	75.47
1993	75.5
1994	75.44
1995	75.32
1996	75.09
1997	74.83
1998	74.56
1999	74.29
2000	73.61
2001	72.93
2002	72.28
2003	71.65
2004	71.05
2005	70.48
2006	69.98
2007	69.51
2008	69.06
2009	68.63
2010	68.22
2011	68.02
2012	67.81
2013	67.57
2014	67.66
2015	67.67
2016	67.72
2017	67.82
2018	67.87
2019	67.9
2020	66.65