Year	Percent
1990	54.46
1991	54.82
1992	55.32
1993	55.6
1994	55.82
1995	56.23
1996	56.54
1997	56.85
1998	57.02
1999	56.96
2000	56.36
2001	55.62
2002	55.24
2003	55.86
2004	56.64
2005	57.26
2006	58.01
2007	58.66
2008	60.12
2009	59.98
2010	60.42
2011	61.65
2012	61.59
2013	61.71
2014	61.97
2015	62.08
2016	62.02
2017	62.34
2018	62.49
2019	62.36
2020	57.39