Year	Percent
1990	45.73
1991	45.8
1992	45.88
1993	45.95
1994	46.03
1995	46.1
1996	46.18
1997	46.25
1998	46.33
1999	46.4
2000	46.48
2001	46.51
2002	46.54
2003	46.57
2004	46.6
2005	46.63
2006	46.66
2007	46.68
2008	46.7
2009	46.72
2010	46.75
2011	46.78
2012	46.8
2013	46.84
2014	46.86
2015	46.88