Year	Percent
1991	58.85
1992	56.79
1993	55.78
1994	54.97
1995	54.33
1996	54.45
1997	55.45
1998	57.73
1999	57.85
2000	58.47
2001	59.08
2002	59.19
2003	58.17
2004	57.68
2005	57.29
2006	57.44
2007	57.33
2008	57.37
2009	55.49
2010	54.48
2011	52.72
2012	50.7
2013	49.62
2014	50.6
2015	51.32
2016	52.04
2017	53.79
2018	55.05
2019	55.44
2020	53.76