Year	Years
1970	11.39
1971	11.46
1972	11.54
1973	11.6
1974	11.66
1975	11.71
1976	11.76
1977	11.81
1978	11.84
1979	11.88
1980	11.91
1981	11.94
1982	11.96
1983	11.98
1984	12
1985	12.02
1986	12.03
1987	12.04
1988	12.05
1989	12.05
1990	12.05
1991	12.05
1992	12.05
1993	12.04
1994	12.03
1995	12.02
1996	12.03
1997	12.05
1998	12.06
1999	12.08
2000	12.11
2001	12.15
2002	12.19
2003	12.24
2004	12.29
2005	12.36
2006	12.43
2007	12.51
2008	12.6
2009	12.7
2010	12.8
2011	12.91
2012	13.02
2013	13.14
2014	13.27
2015	13.39