Year	Percent
1990	75.99
1991	75.86
1992	75.82
1993	75.79
1994	75.78
1995	75.78
1996	75.8
1997	75.77
1998	75.74
1999	75.67
2000	75.57
2001	75.43
2002	75.25
2003	75.16
2004	75.08
2005	75.04
2006	75.01
2007	75
2008	74.98
2009	74.95
2010	74.88
2011	74.79
2012	74.66
2013	74.55
2014	74.45
2015	74.35
2016	74.25
2017	74.16
2018	74.07
2019	73.99