Year	Years
1970	7.83
1971	7.99
1972	8.15
1973	8.32
1974	8.48
1975	8.65
1976	8.82
1977	8.98
1978	9.15
1979	9.32
1980	9.49
1981	9.66
1982	9.83
1983	10
1984	10.17
1985	10.34
1986	10.51
1987	10.67
1988	10.84
1989	11.01
1990	11.18
1991	11.34
1992	11.51
1993	11.67
1994	11.83
1995	12
1996	12.15
1997	12.31
1998	12.47
1999	12.63
2000	12.78
2001	12.93
2002	13.08
2003	13.23
2004	13.38
2005	13.53
2006	13.67
2007	13.82
2008	13.96
2009	14.1
2010	14.24
2011	14.37
2012	14.51
2013	14.64
2014	14.77
2015	14.9