Year	Years
1970	0.87
1971	0.9
1972	0.92
1973	0.95
1974	0.98
1975	1.01
1976	1.04
1977	1.07
1978	1.1
1979	1.13
1980	1.17
1981	1.2
1982	1.24
1983	1.28
1984	1.32
1985	1.36
1986	1.4
1987	1.44
1988	1.49
1989	1.53
1990	1.58
1991	1.63
1992	1.69
1993	1.74
1994	1.8
1995	1.86
1996	1.93
1997	2
1998	2.07
1999	2.14
2000	2.21
2001	2.29
2002	2.36
2003	2.44
2004	2.51
2005	2.59
2006	2.67
2007	2.75
2008	2.83
2009	2.91
2010	2.99
2011	3.08
2012	3.16
2013	3.25
2014	3.33
2015	3.42