Year	Years
1970	0.54
1971	0.55
1972	0.57
1973	0.59
1974	0.62
1975	0.64
1976	0.66
1977	0.68
1978	0.71
1979	0.73
1980	0.76
1981	0.79
1982	0.81
1983	0.84
1984	0.87
1985	0.91
1986	0.94
1987	0.97
1988	1.01
1989	1.04
1990	1.08
1991	1.12
1992	1.16
1993	1.2
1994	1.25
1995	1.29
1996	1.34
1997	1.39
1998	1.44
1999	1.49
2000	1.54
2001	1.59
2002	1.65
2003	1.7
2004	1.76
2005	1.82
2006	1.88
2007	1.94
2008	2
2009	2.06
2010	2.13
2011	2.19
2012	2.26
2013	2.33
2014	2.4
2015	2.47