Year	Years
1970	0.63
1971	0.65
1972	0.68
1973	0.7
1974	0.73
1975	0.75
1976	0.78
1977	0.81
1978	0.84
1979	0.88
1980	0.91
1981	0.95
1982	0.98
1983	1.02
1984	1.06
1985	1.1
1986	1.14
1987	1.19
1988	1.23
1989	1.28
1990	1.33
1991	1.39
1992	1.44
1993	1.5
1994	1.56
1995	1.62
1996	1.69
1997	1.76
1998	1.83
1999	1.9
2000	1.98
2001	2.06
2002	2.14
2003	2.22
2004	2.3
2005	2.38
2006	2.47
2007	2.56
2008	2.65
2009	2.74
2010	2.83
2011	2.92
2012	3.01
2013	3.11
2014	3.2
2015	3.3