Year	Percent
1990	4.14
1991	4.26
1992	4.39
1993	4.51
1994	4.64
1995	4.76
1996	4.89
1997	5.01
1998	5.14
1999	5.26
2000	5.39
2001	5.49
2002	5.59
2003	5.69
2004	5.79
2005	5.89
2006	5.99
2007	6.08
2008	6.18
2009	6.28
2010	6.37
2011	6.44
2012	6.5
2013	6.57
2014	6.63
2015	6.7