Year	Years
1970	9.74
1971	9.9
1972	10.07
1973	10.24
1974	10.4
1975	10.57
1976	10.73
1977	10.9
1978	11.06
1979	11.22
1980	11.38
1981	11.53
1982	11.69
1983	11.84
1984	11.98
1985	12.13
1986	12.27
1987	12.4
1988	12.54
1989	12.67
1990	12.8
1991	12.92
1992	13.04
1993	13.16
1994	13.27
1995	13.38
1996	13.48
1997	13.58
1998	13.67
1999	13.77
2000	13.87
2001	13.97
2002	14.07
2003	14.16
2004	14.26
2005	14.36
2006	14.46
2007	14.55
2008	14.65
2009	14.75
2010	14.84
2011	14.94
2012	15.04
2013	15.13
2014	15.23
2015	15.32