Year	Years
1970	0.59
1971	0.61
1972	0.63
1973	0.65
1974	0.68
1975	0.7
1976	0.73
1977	0.76
1978	0.78
1979	0.81
1980	0.84
1981	0.88
1982	0.91
1983	0.94
1984	0.98
1985	1.01
1986	1.05
1987	1.09
1988	1.13
1989	1.18
1990	1.22
1991	1.27
1992	1.32
1993	1.37
1994	1.42
1995	1.47
1996	1.52
1997	1.57
1998	1.63
1999	1.68
2000	1.74
2001	1.79
2002	1.85
2003	1.91
2004	1.97
2005	2.03
2006	2.1
2007	2.16
2008	2.23
2009	2.29
2010	2.36
2011	2.43
2012	2.5
2013	2.57
2014	2.65
2015	2.72