Year	Years
1970	0.34
1971	0.35
1972	0.37
1973	0.38
1974	0.39
1975	0.41
1976	0.42
1977	0.44
1978	0.45
1979	0.47
1980	0.49
1981	0.5
1982	0.52
1983	0.54
1984	0.56
1985	0.58
1986	0.6
1987	0.63
1988	0.65
1989	0.67
1990	0.7
1991	0.72
1992	0.75
1993	0.78
1994	0.81
1995	0.84
1996	0.88
1997	0.91
1998	0.94
1999	0.98
2000	1.02
2001	1.05
2002	1.09
2003	1.13
2004	1.17
2005	1.21
2006	1.25
2007	1.3
2008	1.34
2009	1.39
2010	1.43
2011	1.48
2012	1.53
2013	1.58
2014	1.64
2015	1.69