Year	Percent
1990	69.34
1991	69.55
1992	69.69
1993	69.62
1994	69.69
1995	69.99
1996	70.29
1997	70.41
1998	70.55
1999	70.8
2000	70.82
2001	71.61
2002	72.42
2003	72.75
2004	72.59
2005	72.33
2006	72.05
2007	71.74
2008	72.08
2009	72.32
2010	72.05
2011	71.6
2012	71.78
2013	71.94
2014	72.08
2015	72.25
2016	72.38
2017	72.49
2018	72.58
2019	72.68