Year	Percent
1990	3.28
1991	3.22
1992	3.17
1993	3.12
1994	3.06
1995	3.01
1996	2.96
1997	2.9
1998	2.85
1999	2.8
2000	2.74
2001	2.69
2002	2.63
2003	2.58
2004	2.52
2005	2.47
2006	2.41
2007	2.36
2008	2.3
2009	2.24
2010	2.19
2011	2.13
2012	2.08
2013	2.02
2014	1.97
2015	1.91