Year	Years
1970	0.73
1971	0.75
1972	0.78
1973	0.8
1974	0.83
1975	0.86
1976	0.89
1977	0.92
1978	0.95
1979	0.98
1980	1.01
1981	1.04
1982	1.08
1983	1.11
1984	1.15
1985	1.19
1986	1.22
1987	1.26
1988	1.31
1989	1.35
1990	1.39
1991	1.44
1992	1.48
1993	1.53
1994	1.58
1995	1.63
1996	1.68
1997	1.73
1998	1.79
1999	1.84
2000	1.9
2001	1.96
2002	2.02
2003	2.08
2004	2.15
2005	2.21
2006	2.28
2007	2.35
2008	2.42
2009	2.49
2010	2.57
2011	2.64
2012	2.72
2013	2.8
2014	2.89
2015	2.97