Year	Percent
1991	59.42
1992	58.03
1993	57.6
1994	58.05
1995	58.3
1996	58.04
1997	58.55
1998	59.32
1999	60.14
2000	60.81
2001	60.65
2002	61.24
2003	61.98
2004	62.19
2005	62.16
2006	62.37
2007	63.01
2008	63.1
2009	61.2
2010	61.25
2011	61.42
2012	61.42
2013	61.54
2014	61.22
2015	61.08
2016	60.91
2017	61.43
2018	61.45
2019	61.86
2020	57.86