Year	Years
1970	0.43
1971	0.45
1972	0.47
1973	0.48
1974	0.5
1975	0.52
1976	0.54
1977	0.56
1978	0.58
1979	0.6
1980	0.63
1981	0.65
1982	0.67
1983	0.7
1984	0.73
1985	0.76
1986	0.79
1987	0.82
1988	0.85
1989	0.88
1990	0.92
1991	0.96
1992	1
1993	1.04
1994	1.08
1995	1.12
1996	1.17
1997	1.21
1998	1.26
1999	1.31
2000	1.35
2001	1.4
2002	1.45
2003	1.5
2004	1.56
2005	1.61
2006	1.67
2007	1.72
2008	1.78
2009	1.84
2010	1.9
2011	1.96
2012	2.02
2013	2.09
2014	2.15
2015	2.22