Year	Years
1970	2.6
1971	2.66
1972	2.73
1973	2.8
1974	2.86
1975	2.93
1976	3.01
1977	3.08
1978	3.15
1979	3.23
1980	3.31
1981	3.39
1982	3.47
1983	3.55
1984	3.63
1985	3.72
1986	3.81
1987	3.9
1988	3.99
1989	4.08
1990	4.17
1991	4.27
1992	4.37
1993	4.47
1994	4.57
1995	4.67
1996	4.78
1997	4.88
1998	4.99
1999	5.1
2000	5.22
2001	5.33
2002	5.44
2003	5.56
2004	5.67
2005	5.79
2006	5.91
2007	6.03
2008	6.15
2009	6.28
2010	6.4
2011	6.53
2012	6.65
2013	6.78
2014	6.91
2015	7.04