Year	Percent
1990	51.17
1991	50.86
1992	50.55
1993	50.24
1994	49.93
1995	49.62
1996	49.3
1997	48.99
1998	48.68
1999	48.37
2000	48.06
2001	47.75
2002	47.44
2003	47.12
2004	46.81
2005	46.5
2006	46.19
2007	45.88
2008	45.57
2009	45.26
2010	44.94
2011	44.63
2012	44.32
2013	44.01
2014	43.7
2015	43.39