Year	Percent
1990	12.71
1991	12.61
1992	12.5
1993	12.39
1994	12.28
1995	12.18
1996	12.07
1997	11.96
1998	11.86
1999	11.75
2000	11.64
2001	11.52
2002	11.4
2003	11.27
2004	11.15
2005	11.03
2006	10.91
2007	10.8
2008	10.68
2009	10.57
2010	10.45
2011	10.34
2012	10.23
2013	10.12
2014	10.02
2015	9.91