Year	Percent
1992	52.22
1993	52.3
1994	52.39
1995	52.48
1996	52.56
1997	52.65
1998	52.74
1999	52.83
2000	52.91
2001	52.96
2002	53
2003	53.04
2004	53.08
2005	53.13
2006	53.04
2007	52.96
2008	52.87
2009	52.79
2010	52.7
2011	52.69
2012	52.68
2013	52.67
2014	52.66
2015	52.65