Year	Years
1970	1.58
1971	1.63
1972	1.69
1973	1.74
1974	1.8
1975	1.86
1976	1.92
1977	1.98
1978	2.04
1979	2.11
1980	2.18
1981	2.25
1982	2.32
1983	2.39
1984	2.47
1985	2.55
1986	2.63
1987	2.71
1988	2.8
1989	2.89
1990	2.98
1991	3.07
1992	3.17
1993	3.27
1994	3.37
1995	3.47
1996	3.59
1997	3.7
1998	3.82
1999	3.93
2000	4.05
2001	4.18
2002	4.3
2003	4.43
2004	4.56
2005	4.69
2006	4.82
2007	4.95
2008	5.09
2009	5.22
2010	5.36
2011	5.5
2012	5.64
2013	5.78
2014	5.92
2015	6.06