Year	Percent
1990	79.14
1991	79.06
1992	79.01
1993	78.96
1994	78.88
1995	78.76
1996	78.59
1997	78.37
1998	78.09
1999	77.76
2000	77.37
2001	76.66
2002	75.85
2003	75.01
2004	74.22
2005	73.55
2006	72.98
2007	72.53
2008	72.15
2009	71.74
2010	71.26
2011	71.06
2012	70.84
2013	70.59
2014	70.3
2015	69.98
2016	69.61
2017	69.19
2018	68.72
2019	68.24
2020	66.82