Year	Years
1970	0.4
1971	0.41
1972	0.43
1973	0.44
1974	0.46
1975	0.48
1976	0.49
1977	0.51
1978	0.53
1979	0.55
1980	0.57
1981	0.59
1982	0.62
1983	0.64
1984	0.67
1985	0.69
1986	0.72
1987	0.75
1988	0.78
1989	0.81
1990	0.85
1991	0.88
1992	0.92
1993	0.96
1994	1
1995	1.05
1996	1.1
1997	1.15
1998	1.2
1999	1.25
2000	1.31
2001	1.36
2002	1.42
2003	1.48
2004	1.54
2005	1.61
2006	1.67
2007	1.74
2008	1.81
2009	1.88
2010	1.95
2011	2.02
2012	2.09
2013	2.16
2014	2.24
2015	2.31