Year	Years
1970	0.28
1971	0.29
1972	0.3
1973	0.31
1974	0.32
1975	0.34
1976	0.35
1977	0.36
1978	0.38
1979	0.39
1980	0.41
1981	0.43
1982	0.44
1983	0.46
1984	0.48
1985	0.5
1986	0.52
1987	0.55
1988	0.57
1989	0.59
1990	0.62
1991	0.65
1992	0.68
1993	0.71
1994	0.74
1995	0.77
1996	0.8
1997	0.83
1998	0.87
1999	0.9
2000	0.94
2001	0.97
2002	1.01
2003	1.04
2004	1.08
2005	1.12
2006	1.16
2007	1.2
2008	1.24
2009	1.28
2010	1.33
2011	1.37
2012	1.42
2013	1.46
2014	1.51
2015	1.56