Year	Years
1970	0.69
1971	0.72
1972	0.74
1973	0.76
1974	0.78
1975	0.81
1976	0.83
1977	0.86
1978	0.88
1979	0.91
1980	0.94
1981	0.97
1982	1
1983	1.03
1984	1.06
1985	1.09
1986	1.12
1987	1.16
1988	1.2
1989	1.23
1990	1.27
1991	1.31
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	1.73
2001	1.79
2002	1.84
2003	1.89
2004	1.95
2005	2.01
2006	2.06
2007	2.12
2008	2.18
2009	2.23
2010	2.29
2011	2.35
2012	2.41
2013	2.47
2014	2.53
2015	2.59