Year	Years
1970	0.85
1971	0.87
1972	0.9
1973	0.93
1974	0.96
1975	0.99
1976	1.02
1977	1.05
1978	1.09
1979	1.12
1980	1.16
1981	1.2
1982	1.24
1983	1.28
1984	1.32
1985	1.37
1986	1.42
1987	1.47
1988	1.53
1989	1.58
1990	1.64
1991	1.71
1992	1.78
1993	1.85
1994	1.92
1995	2
1996	2.06
1997	2.11
1998	2.17
1999	2.23
2000	2.29
2001	2.35
2002	2.41
2003	2.48
2004	2.54
2005	2.61
2006	2.67
2007	2.74
2008	2.81
2009	2.88
2010	2.95
2011	3.03
2012	3.1
2013	3.18
2014	3.26
2015	3.34