Year	Years
1970	0.64
1971	0.66
1972	0.68
1973	0.71
1974	0.73
1975	0.76
1976	0.78
1977	0.81
1978	0.84
1979	0.87
1980	0.9
1981	0.94
1982	0.97
1983	1.01
1984	1.05
1985	1.09
1986	1.13
1987	1.17
1988	1.22
1989	1.27
1990	1.32
1991	1.37
1992	1.43
1993	1.49
1994	1.55
1995	1.62
1996	1.69
1997	1.76
1998	1.83
1999	1.89
2000	1.96
2001	2.04
2002	2.11
2003	2.18
2004	2.25
2005	2.32
2006	2.4
2007	2.47
2008	2.54
2009	2.62
2010	2.69
2011	2.77
2012	2.84
2013	2.91
2014	2.99
2015	3.06