Year	Percent
1990	71.82
1991	72
1992	72.19
1993	72.38
1994	72.57
1995	72.75
1996	72.94
1997	73.13
1998	73.31
1999	73.5
2000	73.69
2001	73.49
2002	73.29
2003	73.09
2004	72.9
2005	72.7
2006	72.86
2007	72.92
2008	73.01
2009	73.06
2010	73.11
2011	73.11
2012	73.11
2013	73.11
2014	73.11
2015	73.11