Year	Years
1970	0.42
1971	0.44
1972	0.45
1973	0.47
1974	0.48
1975	0.5
1976	0.52
1977	0.53
1978	0.55
1979	0.57
1980	0.59
1981	0.61
1982	0.63
1983	0.65
1984	0.67
1985	0.69
1986	0.72
1987	0.74
1988	0.76
1989	0.79
1990	0.81
1991	0.84
1992	0.87
1993	0.9
1994	0.93
1995	0.96
1996	0.99
1997	1.02
1998	1.05
1999	1.08
2000	1.12
2001	1.16
2002	1.19
2003	1.23
2004	1.27
2005	1.31
2006	1.35
2007	1.39
2008	1.44
2009	1.48
2010	1.53
2011	1.58
2012	1.63
2013	1.68
2014	1.73
2015	1.79