Year	Years
1970	1.24
1971	1.27
1972	1.31
1973	1.35
1974	1.39
1975	1.43
1976	1.47
1977	1.51
1978	1.56
1979	1.6
1980	1.65
1981	1.7
1982	1.75
1983	1.8
1984	1.85
1985	1.91
1986	1.96
1987	2.02
1988	2.08
1989	2.15
1990	2.21
1991	2.28
1992	2.35
1993	2.43
1994	2.5
1995	2.58
1996	2.66
1997	2.74
1998	2.82
1999	2.9
2000	2.98
2001	3.07
2002	3.15
2003	3.24
2004	3.32
2005	3.41
2006	3.5
2007	3.59
2008	3.68
2009	3.77
2010	3.86
2011	3.95
2012	4.05
2013	4.14
2014	4.24
2015	4.34