Year	Years
1970	0.74
1971	0.76
1972	0.79
1973	0.81
1974	0.84
1975	0.86
1976	0.89
1977	0.92
1978	0.95
1979	0.98
1980	1
1981	1.03
1982	1.07
1983	1.1
1984	1.13
1985	1.16
1986	1.19
1987	1.22
1988	1.26
1989	1.29
1990	1.33
1991	1.36
1992	1.4
1993	1.43
1994	1.47
1995	1.5
1996	1.54
1997	1.58
1998	1.62
1999	1.67
2000	1.71
2001	1.76
2002	1.81
2003	1.86
2004	1.91
2005	1.97
2006	2.02
2007	2.08
2008	2.14
2009	2.2
2010	2.26
2011	2.32
2012	2.39
2013	2.45
2014	2.52
2015	2.59