Year	Years
1970	9.87
1971	10.01
1972	10.14
1973	10.27
1974	10.4
1975	10.52
1976	10.63
1977	10.75
1978	10.86
1979	10.97
1980	11.07
1981	11.18
1982	11.28
1983	11.37
1984	11.47
1985	11.56
1986	11.65
1987	11.74
1988	11.83
1989	11.92
1990	12
1991	12.09
1992	12.17
1993	12.25
1994	12.34
1995	12.42
1996	12.51
1997	12.61
1998	12.71
1999	12.81
2000	12.92
2001	13.02
2002	13.13
2003	13.25
2004	13.36
2005	13.48
2006	13.6
2007	13.72
2008	13.84
2009	13.97
2010	14.1
2011	14.22
2012	14.35
2013	14.48
2014	14.61
2015	14.74