Year	Years
1970	0.75
1971	0.77
1972	0.79
1973	0.81
1974	0.83
1975	0.86
1976	0.88
1977	0.91
1978	0.93
1979	0.96
1980	0.99
1981	1.01
1982	1.04
1983	1.07
1984	1.1
1985	1.13
1986	1.16
1987	1.2
1988	1.23
1989	1.27
1990	1.3
1991	1.34
1992	1.38
1993	1.42
1994	1.46
1995	1.5
1996	1.54
1997	1.59
1998	1.64
1999	1.69
2000	1.73
2001	1.78
2002	1.83
2003	1.89
2004	1.94
2005	1.99
2006	2.05
2007	2.1
2008	2.16
2009	2.21
2010	2.27
2011	2.33
2012	2.39
2013	2.46
2014	2.52
2015	2.58