Year	Percent
1990	75.96
1991	76.02
1992	76.13
1993	76.25
1994	76.36
1995	76.34
1996	76.18
1997	76.11
1998	76.01
1999	75.82
2000	75.61
2001	75.39
2002	75.15
2003	74.91
2004	74.66
2005	74.41
2006	74.15
2007	73.88
2008	73.62
2009	73.35
2010	73.07
2011	72.77
2012	72.46
2013	72.14
2014	71.81
2015	71.47
2016	71.1
2017	70.71
2018	70.7
2019	70.69