Year	Percent
1990	56.64
1991	56.82
1992	57.02
1993	57.17
1994	57.27
1995	57.34
1996	57.22
1997	57.05
1998	56.89
1999	56.79
2000	56.74
2001	56.96
2002	57.25
2003	57.56
2004	57.84
2005	58.06
2006	57.89
2007	57.67
2008	57.44
2009	57.25
2010	57.13
2011	57.36
2012	57.67
2013	58.03
2014	58.38
2015	58.69
2016	58.88
2017	59.03
2018	59.2
2019	59.36