Year	Years
1970	0.42
1971	0.44
1972	0.45
1973	0.47
1974	0.49
1975	0.51
1976	0.53
1977	0.55
1978	0.57
1979	0.59
1980	0.61
1981	0.64
1982	0.66
1983	0.69
1984	0.72
1985	0.75
1986	0.78
1987	0.81
1988	0.85
1989	0.88
1990	0.92
1991	0.96
1992	1.01
1993	1.05
1994	1.1
1995	1.16
1996	1.21
1997	1.26
1998	1.31
1999	1.37
2000	1.42
2001	1.48
2002	1.53
2003	1.59
2004	1.65
2005	1.71
2006	1.78
2007	1.84
2008	1.91
2009	1.98
2010	2.04
2011	2.11
2012	2.19
2013	2.26
2014	2.33
2015	2.41