Year	Years
1970	0.25
1971	0.26
1972	0.28
1973	0.29
1974	0.3
1975	0.32
1976	0.33
1977	0.35
1978	0.36
1979	0.38
1980	0.4
1981	0.42
1982	0.44
1983	0.46
1984	0.49
1985	0.52
1986	0.54
1987	0.58
1988	0.61
1989	0.65
1990	0.68
1991	0.73
1992	0.77
1993	0.82
1994	0.88
1995	0.94
1996	0.99
1997	1.03
1998	1.08
1999	1.13
2000	1.18
2001	1.23
2002	1.28
2003	1.33
2004	1.39
2005	1.44
2006	1.5
2007	1.56
2008	1.61
2009	1.67
2010	1.73
2011	1.8
2012	1.86
2013	1.92
2014	1.99
2015	2.06