Year	Percent
1991	54.98
1992	54.99
1993	54.97
1994	54.95
1995	54.89
1996	54.5
1997	54.16
1998	53.95
1999	53.9
2000	54.08
2001	53.98
2002	54.02
2003	54.29
2004	54.75
2005	55.3
2006	55.37
2007	55.57
2008	55.9
2009	56.15
2010	56.59
2011	56.48
2012	56.44
2013	56.55
2014	56.87
2015	57.24
2016	56.94
2017	56.79
2018	56.83
2019	57.03
2020	55.24