Year	Years
1970	5.1
1971	5.2
1972	5.31
1973	5.41
1974	5.52
1975	5.63
1976	5.73
1977	5.84
1978	5.95
1979	6.05
1980	6.16
1981	6.27
1982	6.37
1983	6.48
1984	6.58
1985	6.68
1986	6.78
1987	6.88
1988	6.98
1989	7.07
1990	7.17
1991	7.26
1992	7.34
1993	7.42
1994	7.5
1995	7.57
1996	7.67
1997	7.77
1998	7.88
1999	7.99
2000	8.1
2001	8.21
2002	8.32
2003	8.44
2004	8.56
2005	8.68
2006	8.81
2007	8.93
2008	9.06
2009	9.18
2010	9.31
2011	9.44
2012	9.58
2013	9.71
2014	9.84
2015	9.98