Year	Years
1970	0.38
1971	0.39
1972	0.41
1973	0.42
1974	0.44
1975	0.46
1976	0.48
1977	0.5
1978	0.52
1979	0.54
1980	0.56
1981	0.59
1982	0.61
1983	0.64
1984	0.67
1985	0.7
1986	0.73
1987	0.76
1988	0.79
1989	0.83
1990	0.87
1991	0.91
1992	0.95
1993	1
1994	1.04
1995	1.09
1996	1.14
1997	1.19
1998	1.25
1999	1.3
2000	1.35
2001	1.41
2002	1.46
2003	1.52
2004	1.58
2005	1.63
2006	1.69
2007	1.76
2008	1.82
2009	1.88
2010	1.95
2011	2.01
2012	2.08
2013	2.15
2014	2.22
2015	2.29