Year	Years
1970	12.22
1971	12.34
1972	12.44
1973	12.54
1974	12.63
1975	12.72
1976	12.8
1977	12.88
1978	12.95
1979	13.01
1980	13.07
1981	13.12
1982	13.17
1983	13.21
1984	13.25
1985	13.28
1986	13.3
1987	13.33
1988	13.34
1989	13.36
1990	13.37
1991	13.37
1992	13.38
1993	13.38
1994	13.38
1995	13.38
1996	13.39
1997	13.4
1998	13.42
1999	13.45
2000	13.48
2001	13.51
2002	13.55
2003	13.6
2004	13.65
2005	13.71
2006	13.78
2007	13.85
2008	13.93
2009	14.01
2010	14.1
2011	14.19
2012	14.29
2013	14.39
2014	14.49
2015	14.6