Year	Years
1970	0.66
1971	0.68
1972	0.7
1973	0.73
1974	0.75
1975	0.78
1976	0.8
1977	0.83
1978	0.86
1979	0.88
1980	0.91
1981	0.94
1982	0.98
1983	1.01
1984	1.04
1985	1.07
1986	1.11
1987	1.15
1988	1.18
1989	1.22
1990	1.26
1991	1.3
1992	1.35
1993	1.39
1994	1.44
1995	1.48
1996	1.53
1997	1.58
1998	1.63
1999	1.68
2000	1.74
2001	1.79
2002	1.85
2003	1.9
2004	1.96
2005	2.02
2006	2.09
2007	2.15
2008	2.22
2009	2.28
2010	2.35
2011	2.43
2012	2.5
2013	2.57
2014	2.65
2015	2.73