Year	Percent
1990	8.07
1991	8.02
1992	7.96
1993	7.91
1994	7.86
1995	7.81
1996	7.75
1997	7.7
1998	7.65
1999	7.59
2000	7.54
2001	7.49
2002	7.44
2003	7.38
2004	7.33
2005	7.28
2006	7.5
2007	7.72
2008	7.95
2009	8.17
2010	8.39
2011	8.33
2012	8.27
2013	8.21
2014	8.14
2015	8.08