Year	Years
1970	0.39
1971	0.4
1972	0.42
1973	0.43
1974	0.44
1975	0.45
1976	0.47
1977	0.48
1978	0.49
1979	0.51
1980	0.52
1981	0.54
1982	0.55
1983	0.57
1984	0.58
1985	0.6
1986	0.62
1987	0.64
1988	0.65
1989	0.67
1990	0.69
1991	0.71
1992	0.73
1993	0.76
1994	0.78
1995	0.8
1996	0.83
1997	0.85
1998	0.88
1999	0.91
2000	0.93
2001	0.96
2002	0.99
2003	1.02
2004	1.05
2005	1.08
2006	1.11
2007	1.14
2008	1.18
2009	1.21
2010	1.24
2011	1.28
2012	1.32
2013	1.35
2014	1.39
2015	1.43