Year	Percent
1990	48.91
1991	48.81
1992	48.71
1993	48.61
1994	48.51
1995	48.41
1996	48.31
1997	48.21
1998	48.11
1999	48.01
2000	47.91
2001	47.81
2002	47.71
2003	47.61
2004	47.51
2005	47.41
2006	47.31
2007	47.21
2008	47.11
2009	47.01
2010	46.91
2011	46.81
2012	46.71
2013	46.61
2014	46.51
2015	46.41