Year	Years
1970	1.22
1971	1.27
1972	1.33
1973	1.39
1974	1.45
1975	1.51
1976	1.58
1977	1.66
1978	1.73
1979	1.82
1980	1.9
1981	2
1982	2.1
1983	2.2
1984	2.31
1985	2.43
1986	2.55
1987	2.68
1988	2.82
1989	2.96
1990	3.11
1991	3.27
1992	3.43
1993	3.6
1994	3.78
1995	3.95
1996	4.08
1997	4.21
1998	4.33
1999	4.46
2000	4.59
2001	4.71
2002	4.84
2003	4.96
2004	5.09
2005	5.22
2006	5.34
2007	5.47
2008	5.6
2009	5.72
2010	5.85
2011	5.98
2012	6.1
2013	6.23
2014	6.36
2015	6.49