Year	Years
1970	0.83
1971	0.87
1972	0.91
1973	0.96
1974	1.01
1975	1.06
1976	1.12
1977	1.18
1978	1.24
1979	1.31
1980	1.38
1981	1.46
1982	1.54
1983	1.63
1984	1.73
1985	1.83
1986	1.94
1987	2.06
1988	2.19
1989	2.33
1990	2.49
1991	2.65
1992	2.83
1993	3.02
1994	3.22
1995	3.44
1996	3.6
1997	3.76
1998	3.93
1999	4.09
2000	4.25
2001	4.41
2002	4.57
2003	4.73
2004	4.89
2005	5.05
2006	5.21
2007	5.37
2008	5.52
2009	5.68
2010	5.84
2011	6
2012	6.16
2013	6.32
2014	6.48
2015	6.64