Year	Percent
1990	70.89
1991	70.98
1992	71.01
1993	71.04
1994	71.07
1995	71.11
1996	71.14
1997	71.18
1998	71.21
1999	71.23
2000	71.26
2001	71.31
2002	71.36
2003	71.41
2004	71.45
2005	71.49
2006	71.57
2007	71.64
2008	71.71
2009	71.78
2010	71.85
2011	71.94
2012	72.04
2013	71.94
2014	71.82
2015	71.68
2016	71.53
2017	71.37
2018	71.17
2019	70.94