Year	Percent
1992	4.38
1993	4.4
1994	4.41
1995	4.42
1996	4.43
1997	4.44
1998	4.45
1999	4.46
2000	4.47
2001	4.49
2002	4.5
2003	4.51
2004	4.52
2005	4.53
2006	4.33
2007	4.13
2008	3.93
2009	3.73
2010	3.53
2011	3.49
2012	3.45
2013	3.4
2014	3.36
2015	3.32