Year	Percent
1990	75.86
1991	75.9
1992	75.93
1993	75.74
1994	75.9
1995	75.78
1996	75.63
1997	75.52
1998	75.5
1999	75.34
2000	75.2
2001	75.2
2002	75.19
2003	75.13
2004	75.04
2005	74.93
2006	72.96
2007	70.9
2008	68.74
2009	66.5
2010	64.17
2011	61.88
2012	59.55
2013	59.45
2014	59.32
2015	59.18
2016	59.02
2017	58.82
2018	58.58
2019	58.38