Year	Percent
1990	43.68
1991	43.86
1992	44.05
1993	44.24
1994	44.43
1995	44.61
1996	44.8
1997	44.99
1998	45.18
1999	45.37
2000	45.55
2001	45.75
2002	45.95
2003	46.15
2004	46.34
2005	46.54
2006	46.72
2007	46.9
2008	47.08
2009	47.25
2010	47.43
2011	47.59
2012	47.75
2013	47.91
2014	48.06
2015	48.22