Year	Years
1970	0.47
1971	0.49
1972	0.5
1973	0.52
1974	0.54
1975	0.56
1976	0.58
1977	0.6
1978	0.62
1979	0.64
1980	0.66
1981	0.68
1982	0.7
1983	0.73
1984	0.75
1985	0.78
1986	0.8
1987	0.83
1988	0.86
1989	0.89
1990	0.92
1991	0.95
1992	0.98
1993	1.02
1994	1.05
1995	1.09
1996	1.13
1997	1.17
1998	1.21
1999	1.25
2000	1.29
2001	1.33
2002	1.38
2003	1.43
2004	1.47
2005	1.52
2006	1.57
2007	1.62
2008	1.68
2009	1.73
2010	1.79
2011	1.84
2012	1.9
2013	1.96
2014	2.03
2015	2.09