Year	Percent
1990	69.43
1991	69.18
1992	68.95
1993	68.77
1994	68.98
1995	69.21
1996	69.46
1997	69.71
1998	69.94
1999	70.16
2000	70.35
2001	70.6
2002	70.84
2003	71.08
2004	71.31
2005	71.53
2006	71.78
2007	72.03
2008	72.27
2009	72.51
2010	72.74
2011	72.98
2012	73.21
2013	73.25
2014	73.42
2015	73.44
2016	73.5
2017	73.5
2018	73.47
2019	73.47