Year	Percent
1991	61.58
1992	61.65
1993	61.63
1994	61.56
1995	61.52
1996	61.31
1997	61.2
1998	61.1
1999	60.95
2000	60.7
2001	60.62
2002	60.58
2003	60.51
2004	60.43
2005	60.32
2006	60.12
2007	59.88
2008	59.64
2009	59.49
2010	59.22
2011	58.65
2012	58.05
2013	57.54
2014	57.05
2015	56.59
2016	56.24
2017	55.93
2018	55.65
2019	55.39
2020	50.79