Year	Years
1970	0.5
1971	0.52
1972	0.54
1973	0.56
1974	0.59
1975	0.61
1976	0.63
1977	0.66
1978	0.69
1979	0.71
1980	0.74
1981	0.77
1982	0.81
1983	0.84
1984	0.88
1985	0.91
1986	0.95
1987	0.99
1988	1.03
1989	1.08
1990	1.12
1991	1.17
1992	1.22
1993	1.27
1994	1.32
1995	1.37
1996	1.42
1997	1.47
1998	1.52
1999	1.57
2000	1.62
2001	1.67
2002	1.73
2003	1.78
2004	1.84
2005	1.9
2006	1.96
2007	2.02
2008	2.08
2009	2.15
2010	2.22
2011	2.29
2012	2.36
2013	2.43
2014	2.5
2015	2.58