Year	Years
1970	0.48
1971	0.5
1972	0.51
1973	0.53
1974	0.54
1975	0.56
1976	0.57
1977	0.59
1978	0.6
1979	0.62
1980	0.64
1981	0.65
1982	0.67
1983	0.69
1984	0.71
1985	0.73
1986	0.75
1987	0.77
1988	0.79
1989	0.81
1990	0.83
1991	0.85
1992	0.88
1993	0.9
1994	0.92
1995	0.95
1996	0.97
1997	1
1998	1.02
1999	1.05
2000	1.08
2001	1.1
2002	1.13
2003	1.16
2004	1.19
2005	1.22
2006	1.25
2007	1.28
2008	1.32
2009	1.35
2010	1.39
2011	1.42
2012	1.46
2013	1.5
2014	1.53
2015	1.57