Year	Percent
1991	59.89
1992	59.32
1993	58.71
1994	58.9
1995	58.93
1996	58.68
1997	57.92
1998	56.92
1999	55.45
2000	54.86
2001	54.97
2002	55.44
2003	54.89
2004	54.28
2005	54.78
2006	55.08
2007	55.73
2008	55.92
2009	54.7
2010	54.1
2011	54.32
2012	54.57
2013	55.23
2014	55.81
2015	56.61
2016	57.77
2017	58.71
2018	59.41
2019	59.29
2020	57.92