Year	Years
1970	5.1
1971	5.2
1972	5.32
1973	5.43
1974	5.54
1975	5.66
1976	5.77
1977	5.89
1978	6.01
1979	6.12
1980	6.24
1981	6.36
1982	6.48
1983	6.6
1984	6.72
1985	6.84
1986	6.96
1987	7.08
1988	7.2
1989	7.32
1990	7.44
1991	7.56
1992	7.68
1993	7.79
1994	7.91
1995	8.02
1996	8.13
1997	8.24
1998	8.35
1999	8.46
2000	8.57
2001	8.68
2002	8.79
2003	8.91
2004	9.02
2005	9.14
2006	9.26
2007	9.37
2008	9.49
2009	9.62
2010	9.74
2011	9.86
2012	9.99
2013	10.11
2014	10.24
2015	10.37