Year	Years
1970	0.21
1971	0.22
1972	0.22
1973	0.23
1974	0.24
1975	0.25
1976	0.26
1977	0.27
1978	0.28
1979	0.29
1980	0.3
1981	0.31
1982	0.32
1983	0.33
1984	0.35
1985	0.36
1986	0.37
1987	0.39
1988	0.4
1989	0.42
1990	0.44
1991	0.45
1992	0.47
1993	0.49
1994	0.51
1995	0.53
1996	0.56
1997	0.58
1998	0.6
1999	0.63
2000	0.65
2001	0.68
2002	0.7
2003	0.73
2004	0.76
2005	0.78
2006	0.81
2007	0.84
2008	0.87
2009	0.9
2010	0.94
2011	0.97
2012	1
2013	1.04
2014	1.07
2015	1.11