Year	Percent
1990	58.28
1991	58.27
1992	58.26
1993	58.3
1994	58.31
1995	58.31
1996	58.3
1997	58.27
1998	58.22
1999	58.17
2000	58.11
2001	58.07
2002	58.01
2003	57.9
2004	57.78
2005	57.66
2006	57.56
2007	57.45
2008	57.33
2009	57.2
2010	57.04
2011	56.89
2012	56.77
2013	56.59
2014	56.42
2015	56.36
2016	56.31
2017	56.2
2018	56.06
2019	55.9