Year	Percent
1990	57.95
1991	58.52
1992	59.86
1993	60.03
1994	61.63
1995	62.44
1996	62.23
1997	63.35
1998	63.11
1999	62.21
2000	62
2001	61.81
2002	61.88
2003	61.72
2004	61.47
2005	60.72
2006	60.17
2007	59.66
2008	59.03
2009	58.95
2010	58.77
2011	58.42
2012	58.33
2013	58.32
2014	58.31
2015	58.34
2016	58.29
2017	58.17
2018	58.02
2019	57.86
2020	56.56