Year	Years
1970	0.38
1971	0.39
1972	0.4
1973	0.41
1974	0.42
1975	0.44
1976	0.45
1977	0.46
1978	0.48
1979	0.49
1980	0.5
1981	0.52
1982	0.54
1983	0.55
1984	0.57
1985	0.59
1986	0.6
1987	0.62
1988	0.64
1989	0.66
1990	0.68
1991	0.7
1992	0.72
1993	0.75
1994	0.77
1995	0.8
1996	0.82
1997	0.85
1998	0.88
1999	0.9
2000	0.93
2001	0.96
2002	0.99
2003	1.02
2004	1.05
2005	1.08
2006	1.11
2007	1.14
2008	1.17
2009	1.2
2010	1.24
2011	1.27
2012	1.31
2013	1.34
2014	1.38
2015	1.42