Year	Years
1970	0.38
1971	0.39
1972	0.4
1973	0.41
1974	0.43
1975	0.44
1976	0.45
1977	0.46
1978	0.48
1979	0.49
1980	0.51
1981	0.52
1982	0.54
1983	0.55
1984	0.57
1985	0.58
1986	0.6
1987	0.62
1988	0.64
1989	0.66
1990	0.68
1991	0.7
1992	0.72
1993	0.74
1994	0.76
1995	0.79
1996	0.81
1997	0.84
1998	0.87
1999	0.9
2000	0.92
2001	0.95
2002	0.98
2003	1.01
2004	1.04
2005	1.07
2006	1.11
2007	1.14
2008	1.17
2009	1.21
2010	1.24
2011	1.28
2012	1.31
2013	1.35
2014	1.39
2015	1.43