Year	Percent
1990	73.48
1991	73.5
1992	73.51
1993	73.58
1994	73.62
1995	73.64
1996	73.6
1997	73.53
1998	73.42
1999	73.28
2000	73.11
2001	72.91
2002	72.67
2003	72.74
2004	72.74
2005	72.71
2006	72.61
2007	72.48
2008	72.31
2009	72.11
2010	71.9
2011	71.72
2012	71.71
2013	71.68
2014	71.65
2015	71.66
2016	71.68
2017	71.68
2018	71.67
2019	71.66