Year	Years
1970	8.1
1971	8.26
1972	8.43
1973	8.59
1974	8.76
1975	8.93
1976	9.09
1977	9.26
1978	9.43
1979	9.6
1980	9.77
1981	9.94
1982	10.11
1983	10.27
1984	10.44
1985	10.61
1986	10.78
1987	10.95
1988	11.11
1989	11.28
1990	11.45
1991	11.61
1992	11.78
1993	11.94
1994	12.1
1995	12.26
1996	12.42
1997	12.58
1998	12.73
1999	12.89
2000	13.04
2001	13.19
2002	13.35
2003	13.49
2004	13.64
2005	13.79
2006	13.93
2007	14.07
2008	14.21
2009	14.35
2010	14.49
2011	14.62
2012	14.75
2013	14.88
2014	15.01
2015	15.13