Year	Years
1970	0.33
1971	0.34
1972	0.35
1973	0.36
1974	0.37
1975	0.39
1976	0.4
1977	0.41
1978	0.43
1979	0.44
1980	0.46
1981	0.48
1982	0.49
1983	0.51
1984	0.53
1985	0.55
1986	0.56
1987	0.58
1988	0.6
1989	0.63
1990	0.65
1991	0.67
1992	0.69
1993	0.72
1994	0.74
1995	0.77
1996	0.8
1997	0.83
1998	0.85
1999	0.88
2000	0.91
2001	0.95
2002	0.98
2003	1.01
2004	1.04
2005	1.08
2006	1.12
2007	1.15
2008	1.19
2009	1.23
2010	1.27
2011	1.31
2012	1.35
2013	1.4
2014	1.44
2015	1.49