Year	Years
1970	0.85
1971	0.88
1972	0.91
1973	0.94
1974	0.98
1975	1.01
1976	1.05
1977	1.08
1978	1.12
1979	1.16
1980	1.2
1981	1.25
1982	1.29
1983	1.34
1984	1.39
1985	1.44
1986	1.5
1987	1.56
1988	1.62
1989	1.69
1990	1.75
1991	1.83
1992	1.9
1993	1.99
1994	2.07
1995	2.16
1996	2.26
1997	2.36
1998	2.45
1999	2.55
2000	2.64
2001	2.73
2002	2.83
2003	2.92
2004	3.02
2005	3.11
2006	3.21
2007	3.3
2008	3.4
2009	3.49
2010	3.59
2011	3.69
2012	3.78
2013	3.88
2014	3.98
2015	4.08