Year	Years
1970	0.25
1971	0.26
1972	0.27
1973	0.29
1974	0.3
1975	0.31
1976	0.33
1977	0.34
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	0.55
1987	0.58
1988	0.61
1989	0.65
1990	0.69
1991	0.73
1992	0.78
1993	0.83
1994	0.89
1995	0.95
1996	1.01
1997	1.07
1998	1.14
1999	1.2
2000	1.26
2001	1.33
2002	1.39
2003	1.46
2004	1.53
2005	1.6
2006	1.66
2007	1.74
2008	1.81
2009	1.88
2010	1.95
2011	2.03
2012	2.11
2013	2.19
2014	2.26
2015	2.35