Year	Years
1970	0.24
1971	0.25
1972	0.26
1973	0.27
1974	0.27
1975	0.28
1976	0.29
1977	0.3
1978	0.32
1979	0.33
1980	0.34
1981	0.35
1982	0.36
1983	0.38
1984	0.39
1985	0.4
1986	0.42
1987	0.43
1988	0.45
1989	0.46
1990	0.48
1991	0.5
1992	0.51
1993	0.53
1994	0.55
1995	0.57
1996	0.59
1997	0.62
1998	0.64
1999	0.66
2000	0.69
2001	0.71
2002	0.74
2003	0.76
2004	0.79
2005	0.82
2006	0.85
2007	0.88
2008	0.91
2009	0.94
2010	0.97
2011	1
2012	1.04
2013	1.07
2014	1.11
2015	1.14