Year	Years
1970	0.58
1971	0.6
1972	0.62
1973	0.64
1974	0.66
1975	0.69
1976	0.71
1977	0.74
1978	0.77
1979	0.8
1980	0.83
1981	0.86
1982	0.9
1983	0.93
1984	0.97
1985	1.01
1986	1.06
1987	1.11
1988	1.16
1989	1.21
1990	1.27
1991	1.34
1992	1.41
1993	1.48
1994	1.57
1995	1.66
1996	1.73
1997	1.81
1998	1.89
1999	1.97
2000	2.05
2001	2.14
2002	2.22
2003	2.3
2004	2.39
2005	2.47
2006	2.56
2007	2.64
2008	2.73
2009	2.82
2010	2.91
2011	2.99
2012	3.08
2013	3.17
2014	3.26
2015	3.35