Year	Percent
1990	58.22
1991	58.19
1992	58.17
1993	58.3
1994	57.92
1995	57.64
1996	57.36
1997	57.05
1998	57.06
1999	57.03
2000	57.11
2001	57.24
2002	57.33
2003	57.39
2004	57.59
2005	57.89
2006	58.11
2007	58.41
2008	58.62
2009	58.78
2010	58.89
2011	58.97
2012	59.01
2013	59.02
2014	59
2015	58.93
2016	58.85
2017	58.76
2018	58.63
2019	58.49