Year	Years
1970	0.61
1971	0.64
1972	0.66
1973	0.69
1974	0.72
1975	0.75
1976	0.78
1977	0.81
1978	0.84
1979	0.88
1980	0.91
1981	0.95
1982	0.99
1983	1.03
1984	1.08
1985	1.12
1986	1.17
1987	1.23
1988	1.28
1989	1.34
1990	1.4
1991	1.46
1992	1.53
1993	1.6
1994	1.68
1995	1.75
1996	1.83
1997	1.9
1998	1.97
1999	2.05
2000	2.12
2001	2.2
2002	2.28
2003	2.35
2004	2.43
2005	2.52
2006	2.6
2007	2.68
2008	2.77
2009	2.86
2010	2.94
2011	3.04
2012	3.13
2013	3.22
2014	3.32
2015	3.41