Year	Percent
1991	58.85
1992	58.63
1993	58.51
1994	58.4
1995	58.28
1996	58.15
1997	58.03
1998	57.93
1999	57.87
2000	57.78
2001	57.76
2002	57.57
2003	57.54
2004	57.5
2005	57.53
2006	57.64
2007	57.73
2008	57.78
2009	57.69
2010	57.65
2011	57.69
2012	55.37
2013	53.06
2014	52.06
2015	51.59
2016	49.44
2017	49.6
2018	50.39
2019	51.1
2020	48.61