Year	Years
1970	0.75
1971	0.78
1972	0.81
1973	0.84
1974	0.87
1975	0.9
1976	0.94
1977	0.98
1978	1.01
1979	1.05
1980	1.1
1981	1.14
1982	1.19
1983	1.23
1984	1.28
1985	1.34
1986	1.39
1987	1.45
1988	1.51
1989	1.58
1990	1.64
1991	1.71
1992	1.79
1993	1.87
1994	1.95
1995	2.03
1996	2.12
1997	2.2
1998	2.29
1999	2.38
2000	2.47
2001	2.56
2002	2.65
2003	2.75
2004	2.84
2005	2.94
2006	3.04
2007	3.14
2008	3.24
2009	3.34
2010	3.45
2011	3.55
2012	3.66
2013	3.76
2014	3.87
2015	3.98