Year	Percent
1991	73.43
1992	73.4
1993	73.2
1994	73.21
1995	73.15
1996	73.14
1997	73.19
1998	73.24
1999	73.22
2000	73.2
2001	73.14
2002	73
2003	72.88
2004	72.81
2005	72.81
2006	72.91
2007	73.03
2008	73.1
2009	72.96
2010	72.95
2011	73
2012	73.03
2013	73.03
2014	72.9
2015	72.76
2016	72.59
2017	72.45
2018	72.31
2019	72.11
2020	70.73