Year	Years
1970	0.26
1971	0.27
1972	0.29
1973	0.3
1974	0.31
1975	0.32
1976	0.34
1977	0.35
1978	0.37
1979	0.39
1980	0.41
1981	0.43
1982	0.45
1983	0.47
1984	0.5
1985	0.52
1986	0.55
1987	0.58
1988	0.62
1989	0.65
1990	0.7
1991	0.74
1992	0.79
1993	0.84
1994	0.9
1995	0.96
1996	1
1997	1.04
1998	1.08
1999	1.11
2000	1.16
2001	1.2
2002	1.24
2003	1.28
2004	1.33
2005	1.37
2006	1.42
2007	1.47
2008	1.52
2009	1.57
2010	1.62
2011	1.68
2012	1.73
2013	1.79
2014	1.85
2015	1.91