Year	Years
1970	0.51
1971	0.53
1972	0.55
1973	0.57
1974	0.6
1975	0.62
1976	0.64
1977	0.67
1978	0.7
1979	0.72
1980	0.75
1981	0.78
1982	0.81
1983	0.84
1984	0.88
1985	0.91
1986	0.95
1987	0.99
1988	1.03
1989	1.07
1990	1.11
1991	1.16
1992	1.2
1993	1.25
1994	1.3
1995	1.35
1996	1.41
1997	1.47
1998	1.53
1999	1.59
2000	1.65
2001	1.71
2002	1.78
2003	1.84
2004	1.91
2005	1.97
2006	2.04
2007	2.11
2008	2.18
2009	2.24
2010	2.31
2011	2.38
2012	2.45
2013	2.52
2014	2.59
2015	2.66