Year	Years
1970	0.72
1971	0.75
1972	0.77
1973	0.8
1974	0.83
1975	0.85
1976	0.88
1977	0.91
1978	0.94
1979	0.98
1980	1.01
1981	1.05
1982	1.08
1983	1.12
1984	1.16
1985	1.2
1986	1.25
1987	1.3
1988	1.34
1989	1.4
1990	1.45
1991	1.51
1992	1.56
1993	1.63
1994	1.69
1995	1.76
1996	1.83
1997	1.9
1998	1.97
1999	2.04
2000	2.12
2001	2.19
2002	2.26
2003	2.33
2004	2.4
2005	2.48
2006	2.55
2007	2.63
2008	2.7
2009	2.78
2010	2.85
2011	2.93
2012	3.01
2013	3.09
2014	3.17
2015	3.25