Year	Years
1970	1.34
1971	1.39
1972	1.44
1973	1.5
1974	1.55
1975	1.61
1976	1.67
1977	1.73
1978	1.79
1979	1.86
1980	1.93
1981	2
1982	2.08
1983	2.16
1984	2.24
1985	2.32
1986	2.41
1987	2.5
1988	2.6
1989	2.69
1990	2.8
1991	2.9
1992	3.01
1993	3.13
1994	3.25
1995	3.37
1996	3.47
1997	3.58
1998	3.68
1999	3.78
2000	3.89
2001	4
2002	4.1
2003	4.21
2004	4.33
2005	4.44
2006	4.55
2007	4.67
2008	4.79
2009	4.91
2010	5.03
2011	5.16
2012	5.28
2013	5.41
2014	5.54
2015	5.67