Year	Years
1970	0.87
1971	0.9
1972	0.94
1973	0.97
1974	1.01
1975	1.04
1976	1.08
1977	1.12
1978	1.16
1979	1.2
1980	1.25
1981	1.29
1982	1.34
1983	1.39
1984	1.44
1985	1.49
1986	1.55
1987	1.6
1988	1.66
1989	1.72
1990	1.78
1991	1.85
1992	1.91
1993	1.98
1994	2.05
1995	2.12
1996	2.19
1997	2.25
1998	2.32
1999	2.39
2000	2.46
2001	2.54
2002	2.61
2003	2.69
2004	2.76
2005	2.84
2006	2.92
2007	3
2008	3.09
2009	3.17
2010	3.26
2011	3.34
2012	3.43
2013	3.52
2014	3.62
2015	3.71