Year	Years
1970	0.61
1971	0.63
1972	0.65
1973	0.68
1974	0.7
1975	0.72
1976	0.74
1977	0.77
1978	0.79
1979	0.82
1980	0.85
1981	0.87
1982	0.9
1983	0.93
1984	0.96
1985	0.99
1986	1.03
1987	1.06
1988	1.09
1989	1.13
1990	1.16
1991	1.2
1992	1.24
1993	1.28
1994	1.32
1995	1.36
1996	1.4
1997	1.45
1998	1.49
1999	1.54
2000	1.59
2001	1.64
2002	1.69
2003	1.74
2004	1.8
2005	1.85
2006	1.91
2007	1.97
2008	2.03
2009	2.09
2010	2.16
2011	2.22
2012	2.29
2013	2.36
2014	2.43
2015	2.5