Year	Years
1970	0.32
1971	0.33
1972	0.34
1973	0.36
1974	0.37
1975	0.38
1976	0.4
1977	0.41
1978	0.43
1979	0.44
1980	0.46
1981	0.47
1982	0.49
1983	0.51
1984	0.52
1985	0.54
1986	0.56
1987	0.58
1988	0.59
1989	0.61
1990	0.63
1991	0.65
1992	0.67
1993	0.69
1994	0.7
1995	0.72
1996	0.74
1997	0.76
1998	0.78
1999	0.8
2000	0.82
2001	0.84
2002	0.86
2003	0.88
2004	0.9
2005	0.93
2006	0.95
2007	0.98
2008	1
2009	1.03
2010	1.06
2011	1.08
2012	1.11
2013	1.14
2014	1.17
2015	1.21