Year	Years
1970	0.23
1971	0.24
1972	0.25
1973	0.25
1974	0.26
1975	0.27
1976	0.28
1977	0.29
1978	0.3
1979	0.31
1980	0.32
1981	0.33
1982	0.34
1983	0.35
1984	0.37
1985	0.38
1986	0.39
1987	0.4
1988	0.42
1989	0.43
1990	0.45
1991	0.46
1992	0.48
1993	0.49
1994	0.51
1995	0.53
1996	0.54
1997	0.56
1998	0.58
1999	0.6
2000	0.62
2001	0.64
2002	0.66
2003	0.68
2004	0.7
2005	0.73
2006	0.75
2007	0.78
2008	0.8
2009	0.83
2010	0.85
2011	0.88
2012	0.91
2013	0.94
2014	0.97
2015	1