Year	Years
1970	0.61
1971	0.63
1972	0.66
1973	0.68
1974	0.71
1975	0.73
1976	0.76
1977	0.79
1978	0.82
1979	0.85
1980	0.88
1981	0.92
1982	0.95
1983	0.99
1984	1.03
1985	1.07
1986	1.11
1987	1.15
1988	1.2
1989	1.25
1990	1.3
1991	1.35
1992	1.4
1993	1.46
1994	1.52
1995	1.59
1996	1.65
1997	1.71
1998	1.78
1999	1.84
2000	1.91
2001	1.98
2002	2.05
2003	2.12
2004	2.19
2005	2.27
2006	2.34
2007	2.42
2008	2.5
2009	2.58
2010	2.66
2011	2.75
2012	2.83
2013	2.92
2014	3.01
2015	3.1