Year	Percent
1990	69.93
1991	70.07
1992	70.08
1993	69.83
1994	69.93
1995	69.98
1996	70.13
1997	70.45
1998	70.68
1999	70.8
2000	71.04
2001	71.28
2002	71.5
2003	71.81
2004	72.18
2005	72.42
2006	72.72
2007	73
2008	73.26
2009	73.47
2010	73.72
2011	73.96
2012	74.08
2013	74.2
2014	74.25
2015	74.24
2016	74.13
2017	74.28
2018	74.47
2019	74.57