Year	Percent
1990	74.27
1991	74.2
1992	74.16
1993	74.08
1994	73.96
1995	73.77
1996	73.6
1997	73.4
1998	73.45
1999	73.25
2000	73.05
2001	72.93
2002	72.84
2003	72.75
2004	72.64
2005	72.52
2006	72.48
2007	72.43
2008	72.41
2009	72.4
2010	72.41
2011	72.45
2012	72.57
2013	72.65
2014	72.74
2015	72.78
2016	72.83
2017	72.87
2018	72.9
2019	72.89