Year	Percent
1991	70.09
1992	71.29
1993	72.09
1994	72.56
1995	73.07
1996	73.24
1997	73.43
1998	72.94
1999	71.83
2000	71.54
2001	71.17
2002	71.18
2003	71.34
2004	71.5
2005	71.42
2006	71.76
2007	72.02
2008	71.73
2009	71.53
2010	71.57
2011	71.58
2012	71.58
2013	71.62
2014	71.73
2015	71.99
2016	71.76
2017	72.22
2018	72.72
2019	72.38