Year	Years
1970	0.42
1971	0.44
1972	0.45
1973	0.46
1974	0.47
1975	0.49
1976	0.5
1977	0.51
1978	0.53
1979	0.54
1980	0.56
1981	0.57
1982	0.59
1983	0.61
1984	0.62
1985	0.64
1986	0.66
1987	0.68
1988	0.69
1989	0.71
1990	0.73
1991	0.75
1992	0.77
1993	0.8
1994	0.82
1995	0.84
1996	0.86
1997	0.89
1998	0.91
1999	0.93
2000	0.96
2001	0.98
2002	1.01
2003	1.04
2004	1.07
2005	1.1
2006	1.12
2007	1.15
2008	1.19
2009	1.22
2010	1.25
2011	1.28
2012	1.32
2013	1.35
2014	1.39
2015	1.42