Year	Percent
1990	13.2
1991	13.08
1992	12.96
1993	12.83
1994	12.71
1995	12.59
1996	12.47
1997	12.35
1998	12.22
1999	12.1
2000	11.98
2001	11.86
2002	11.73
2003	11.61
2004	11.49
2005	11.37
2006	11.24
2007	11.12
2008	11
2009	10.88
2010	10.75
2011	10.63
2012	10.51
2013	10.39
2014	10.27
2015	10.14