Year	Years
1970	1.77
1971	1.83
1972	1.89
1973	1.95
1974	2.01
1975	2.07
1976	2.14
1977	2.2
1978	2.27
1979	2.34
1980	2.41
1981	2.49
1982	2.56
1983	2.64
1984	2.72
1985	2.8
1986	2.89
1987	2.98
1988	3.07
1989	3.16
1990	3.25
1991	3.35
1992	3.44
1993	3.55
1994	3.65
1995	3.75
1996	3.86
1997	3.97
1998	4.08
1999	4.19
2000	4.3
2001	4.42
2002	4.54
2003	4.66
2004	4.78
2005	4.91
2006	5.04
2007	5.16
2008	5.3
2009	5.43
2010	5.56
2011	5.7
2012	5.84
2013	5.98
2014	6.13
2015	6.27