Year	Years
1970	10.22
1971	10.39
1972	10.57
1973	10.74
1974	10.91
1975	11.07
1976	11.24
1977	11.4
1978	11.56
1979	11.71
1980	11.86
1981	12
1982	12.15
1983	12.28
1984	12.41
1985	12.54
1986	12.67
1987	12.79
1988	12.9
1989	13.01
1990	13.12
1991	13.23
1992	13.33
1993	13.42
1994	13.51
1995	13.6
1996	13.68
1997	13.77
1998	13.85
1999	13.93
2000	14.02
2001	14.1
2002	14.19
2003	14.27
2004	14.36
2005	14.45
2006	14.53
2007	14.62
2008	14.71
2009	14.8
2010	14.89
2011	14.98
2012	15.07
2013	15.16
2014	15.26
2015	15.35