Year	Years
1970	0.83
1971	0.86
1972	0.9
1973	0.94
1974	0.98
1975	1.02
1976	1.06
1977	1.11
1978	1.16
1979	1.22
1980	1.27
1981	1.34
1982	1.4
1983	1.47
1984	1.55
1985	1.63
1986	1.72
1987	1.82
1988	1.92
1989	2.03
1990	2.14
1991	2.26
1992	2.39
1993	2.52
1994	2.66
1995	2.79
1996	2.89
1997	2.98
1998	3.07
1999	3.17
2000	3.26
2001	3.36
2002	3.45
2003	3.55
2004	3.64
2005	3.74
2006	3.84
2007	3.94
2008	4.04
2009	4.14
2010	4.24
2011	4.35
2012	4.45
2013	4.56
2014	4.66
2015	4.77