Year	Years
1970	0.78
1971	0.81
1972	0.83
1973	0.86
1974	0.89
1975	0.92
1976	0.95
1977	0.98
1978	1.02
1979	1.05
1980	1.08
1981	1.12
1982	1.16
1983	1.2
1984	1.24
1985	1.28
1986	1.32
1987	1.37
1988	1.41
1989	1.46
1990	1.51
1991	1.56
1992	1.61
1993	1.67
1994	1.72
1995	1.78
1996	1.85
1997	1.91
1998	1.98
1999	2.04
2000	2.11
2001	2.18
2002	2.26
2003	2.33
2004	2.41
2005	2.49
2006	2.57
2007	2.65
2008	2.73
2009	2.82
2010	2.9
2011	2.99
2012	3.08
2013	3.18
2014	3.27
2015	3.37