Year	Years
1970	0.44
1971	0.46
1972	0.48
1973	0.5
1974	0.52
1975	0.53
1976	0.56
1977	0.58
1978	0.6
1979	0.62
1980	0.65
1981	0.67
1982	0.7
1983	0.72
1984	0.75
1985	0.78
1986	0.81
1987	0.85
1988	0.88
1989	0.91
1990	0.95
1991	0.99
1992	1.03
1993	1.07
1994	1.12
1995	1.16
1996	1.21
1997	1.25
1998	1.3
1999	1.34
2000	1.39
2001	1.44
2002	1.49
2003	1.54
2004	1.59
2005	1.64
2006	1.7
2007	1.75
2008	1.81
2009	1.87
2010	1.93
2011	1.99
2012	2.05
2013	2.11
2014	2.18
2015	2.25