Year	Years
1970	5.5
1971	5.6
1972	5.71
1973	5.81
1974	5.91
1975	6.01
1976	6.11
1977	6.21
1978	6.32
1979	6.42
1980	6.52
1981	6.62
1982	6.72
1983	6.81
1984	6.91
1985	7.01
1986	7.1
1987	7.19
1988	7.28
1989	7.37
1990	7.46
1991	7.54
1992	7.62
1993	7.7
1994	7.77
1995	7.85
1996	7.95
1997	8.06
1998	8.17
1999	8.28
2000	8.39
2001	8.51
2002	8.63
2003	8.75
2004	8.87
2005	8.99
2006	9.12
2007	9.24
2008	9.37
2009	9.5
2010	9.63
2011	9.76
2012	9.89
2013	10.03
2014	10.16
2015	10.29