Year	Years
1970	0.56
1971	0.58
1972	0.6
1973	0.62
1974	0.64
1975	0.67
1976	0.69
1977	0.72
1978	0.74
1979	0.77
1980	0.79
1981	0.82
1982	0.85
1983	0.88
1984	0.91
1985	0.95
1986	0.98
1987	1.01
1988	1.05
1989	1.09
1990	1.13
1991	1.17
1992	1.21
1993	1.25
1994	1.3
1995	1.35
1996	1.4
1997	1.45
1998	1.5
1999	1.55
2000	1.61
2001	1.66
2002	1.72
2003	1.78
2004	1.84
2005	1.9
2006	1.96
2007	2.03
2008	2.09
2009	2.16
2010	2.23
2011	2.29
2012	2.37
2013	2.44
2014	2.51
2015	2.59