Year	Years
1970	4.9
1971	5.03
1972	5.16
1973	5.29
1974	5.43
1975	5.57
1976	5.7
1977	5.85
1978	5.99
1979	6.14
1980	6.28
1981	6.43
1982	6.58
1983	6.74
1984	6.89
1985	7.05
1986	7.2
1987	7.36
1988	7.52
1989	7.68
1990	7.84
1991	8.01
1992	8.17
1993	8.33
1994	8.49
1995	8.66
1996	8.81
1997	8.97
1998	9.13
1999	9.28
2000	9.44
2001	9.6
2002	9.76
2003	9.92
2004	10.08
2005	10.24
2006	10.4
2007	10.56
2008	10.72
2009	10.88
2010	11.04
2011	11.2
2012	11.36
2013	11.52
2014	11.68
2015	11.84