Year	Percent
1990	52.35
1991	52.71
1992	53.04
1993	53.31
1994	53.59
1995	53.79
1996	53.97
1997	54.14
1998	54.29
1999	54.44
2000	54.65
2001	54.8
2002	54.95
2003	55.13
2004	55.33
2005	55.49
2006	55.67
2007	55.84
2008	56
2009	56.14
2010	56.3
2011	56.47
2012	56.62
2013	56.75
2014	56.84
2015	56.88
2016	56.83
2017	56.86
2018	56.88
2019	56.83