Year	Years
1970	0.31
1971	0.31
1972	0.32
1973	0.33
1974	0.34
1975	0.35
1976	0.36
1977	0.37
1978	0.38
1979	0.39
1980	0.41
1981	0.42
1982	0.43
1983	0.44
1984	0.45
1985	0.47
1986	0.48
1987	0.49
1988	0.51
1989	0.52
1990	0.54
1991	0.55
1992	0.57
1993	0.59
1994	0.6
1995	0.62
1996	0.64
1997	0.66
1998	0.68
1999	0.7
2000	0.72
2001	0.74
2002	0.76
2003	0.78
2004	0.8
2005	0.83
2006	0.85
2007	0.87
2008	0.9
2009	0.92
2010	0.95
2011	0.97
2012	1
2013	1.03
2014	1.06
2015	1.09