Year	Years
1970	0.48
1971	0.5
1972	0.52
1973	0.55
1974	0.57
1975	0.6
1976	0.62
1977	0.65
1978	0.68
1979	0.71
1980	0.75
1981	0.78
1982	0.82
1983	0.86
1984	0.91
1985	0.95
1986	1
1987	1.06
1988	1.12
1989	1.18
1990	1.25
1991	1.33
1992	1.41
1993	1.5
1994	1.6
1995	1.71
1996	1.8
1997	1.9
1998	1.99
1999	2.08
2000	2.17
2001	2.27
2002	2.36
2003	2.46
2004	2.56
2005	2.65
2006	2.75
2007	2.85
2008	2.95
2009	3.05
2010	3.16
2011	3.26
2012	3.36
2013	3.47
2014	3.58
2015	3.68