Year	Years
1970	0.61
1971	0.63
1972	0.65
1973	0.68
1974	0.7
1975	0.72
1976	0.74
1977	0.77
1978	0.79
1979	0.82
1980	0.85
1981	0.88
1982	0.9
1983	0.93
1984	0.96
1985	1
1986	1.03
1987	1.06
1988	1.1
1989	1.13
1990	1.17
1991	1.21
1992	1.24
1993	1.28
1994	1.33
1995	1.37
1996	1.41
1997	1.46
1998	1.5
1999	1.55
2000	1.6
2001	1.65
2002	1.7
2003	1.75
2004	1.81
2005	1.86
2006	1.92
2007	1.98
2008	2.04
2009	2.1
2010	2.17
2011	2.24
2012	2.3
2013	2.37
2014	2.44
2015	2.52