Year	Years
1970	0.77
1971	0.79
1972	0.82
1973	0.85
1974	0.88
1975	0.91
1976	0.95
1977	0.98
1978	1.02
1979	1.05
1980	1.09
1981	1.13
1982	1.17
1983	1.21
1984	1.26
1985	1.3
1986	1.35
1987	1.4
1988	1.45
1989	1.5
1990	1.56
1991	1.62
1992	1.68
1993	1.74
1994	1.8
1995	1.87
1996	1.94
1997	2
1998	2.07
1999	2.14
2000	2.21
2001	2.29
2002	2.36
2003	2.44
2004	2.52
2005	2.6
2006	2.68
2007	2.77
2008	2.85
2009	2.94
2010	3.03
2011	3.12
2012	3.21
2013	3.3
2014	3.4
2015	3.49