Year	Years
1970	0.33
1971	0.35
1972	0.36
1973	0.37
1974	0.38
1975	0.4
1976	0.41
1977	0.43
1978	0.44
1979	0.46
1980	0.48
1981	0.5
1982	0.52
1983	0.53
1984	0.55
1985	0.58
1986	0.6
1987	0.62
1988	0.65
1989	0.67
1990	0.7
1991	0.72
1992	0.75
1993	0.78
1994	0.81
1995	0.85
1996	0.88
1997	0.92
1998	0.96
1999	1
2000	1.04
2001	1.08
2002	1.12
2003	1.16
2004	1.21
2005	1.25
2006	1.3
2007	1.34
2008	1.39
2009	1.44
2010	1.49
2011	1.54
2012	1.59
2013	1.64
2014	1.7
2015	1.75