Year	Percent
1990	53.21
1991	53.36
1992	53.5
1993	53.64
1994	53.78
1995	53.92
1996	54.08
1997	54.22
1998	54.35
1999	54.48
2000	54.61
2001	54.72
2002	54.82
2003	54.92
2004	55.03
2005	55.15
2006	55.29
2007	55.44
2008	55.61
2009	55.77
2010	56.15
2011	56.49
2012	56.84
2013	58.01
2014	55.36
2015	55.77
2016	56.2
2017	56.64
2018	56.44
2019	56.27