Year	Percent
1991	75.4
1992	75.42
1993	75.3
1994	75.19
1995	75.04
1996	75.1
1997	75.09
1998	75.01
1999	74.88
2000	74.83
2001	74.88
2002	74.87
2003	74.88
2004	74.92
2005	74.98
2006	75.1
2007	74.92
2008	74.6
2009	73.97
2010	72.44
2011	70.83
2012	70.29
2013	69.63
2014	69.92
2015	69.79
2016	69.54
2017	69.27
2018	68.94
2019	68.57