Year	Years
1970	0.75
1971	0.77
1972	0.79
1973	0.81
1974	0.84
1975	0.86
1976	0.88
1977	0.91
1978	0.94
1979	0.96
1980	0.99
1981	1.02
1982	1.05
1983	1.08
1984	1.11
1985	1.14
1986	1.17
1987	1.21
1988	1.24
1989	1.28
1990	1.32
1991	1.35
1992	1.39
1993	1.44
1994	1.48
1995	1.52
1996	1.57
1997	1.62
1998	1.67
1999	1.72
2000	1.77
2001	1.82
2002	1.87
2003	1.93
2004	1.98
2005	2.03
2006	2.09
2007	2.15
2008	2.21
2009	2.27
2010	2.33
2011	2.39
2012	2.45
2013	2.51
2014	2.58
2015	2.64