Year	Years
1970	0.41
1971	0.42
1972	0.44
1973	0.45
1974	0.46
1975	0.47
1976	0.49
1977	0.5
1978	0.52
1979	0.53
1980	0.55
1981	0.56
1982	0.58
1983	0.6
1984	0.62
1985	0.63
1986	0.65
1987	0.67
1988	0.69
1989	0.71
1990	0.73
1991	0.76
1992	0.78
1993	0.8
1994	0.83
1995	0.86
1996	0.88
1997	0.91
1998	0.94
1999	0.97
2000	1
2001	1.03
2002	1.06
2003	1.09
2004	1.13
2005	1.16
2006	1.19
2007	1.23
2008	1.26
2009	1.3
2010	1.33
2011	1.37
2012	1.41
2013	1.45
2014	1.49
2015	1.53