Year	Years
1970	0.87
1971	0.9
1972	0.93
1973	0.95
1974	0.98
1975	1.01
1976	1.05
1977	1.08
1978	1.11
1979	1.15
1980	1.18
1981	1.22
1982	1.26
1983	1.3
1984	1.34
1985	1.39
1986	1.43
1987	1.48
1988	1.53
1989	1.58
1990	1.63
1991	1.69
1992	1.75
1993	1.81
1994	1.87
1995	1.94
1996	2
1997	2.06
1998	2.12
1999	2.19
2000	2.26
2001	2.32
2002	2.39
2003	2.46
2004	2.53
2005	2.6
2006	2.67
2007	2.74
2008	2.81
2009	2.89
2010	2.96
2011	3.04
2012	3.11
2013	3.19
2014	3.27
2015	3.35