Year	Years
1970	0.38
1971	0.4
1972	0.42
1973	0.43
1974	0.45
1975	0.47
1976	0.5
1977	0.52
1978	0.54
1979	0.57
1980	0.59
1981	0.62
1982	0.65
1983	0.68
1984	0.72
1985	0.75
1986	0.79
1987	0.82
1988	0.86
1989	0.91
1990	0.95
1991	1
1992	1.04
1993	1.09
1994	1.15
1995	1.2
1996	1.26
1997	1.32
1998	1.38
1999	1.44
2000	1.51
2001	1.57
2002	1.64
2003	1.71
2004	1.78
2005	1.84
2006	1.91
2007	1.98
2008	2.04
2009	2.1
2010	2.17
2011	2.23
2012	2.29
2013	2.34
2014	2.4
2015	2.46