Year	Years
1970	0.67
1971	0.69
1972	0.71
1973	0.73
1974	0.75
1975	0.77
1976	0.79
1977	0.81
1978	0.83
1979	0.85
1980	0.88
1981	0.9
1982	0.93
1983	0.95
1984	0.98
1985	1
1986	1.03
1987	1.06
1988	1.09
1989	1.12
1990	1.15
1991	1.18
1992	1.21
1993	1.24
1994	1.27
1995	1.31
1996	1.34
1997	1.38
1998	1.41
1999	1.45
2000	1.49
2001	1.53
2002	1.57
2003	1.61
2004	1.65
2005	1.69
2006	1.74
2007	1.78
2008	1.83
2009	1.88
2010	1.92
2011	1.97
2012	2.02
2013	2.08
2014	2.13
2015	2.18