Year	Percent
1990	58.9
1991	58.96
1992	59.2
1993	59.47
1994	59.64
1995	59.77
1996	59.94
1997	59.84
1998	59.61
1999	59.28
2000	58.87
2001	58.44
2002	58.02
2003	57.54
2004	57.12
2005	56.78
2006	56.54
2007	56.38
2008	56.5
2009	56.58
2010	56.57
2011	56.59
2012	56.53
2013	56.32
2014	56.04
2015	55.71
2016	55.35
2017	54.99
2018	54.62
2019	54.24
2020	53.03