Year	Years
1970	0.53
1971	0.55
1972	0.57
1973	0.59
1974	0.61
1975	0.63
1976	0.65
1977	0.67
1978	0.7
1979	0.72
1980	0.75
1981	0.77
1982	0.8
1983	0.83
1984	0.85
1985	0.88
1986	0.91
1987	0.95
1988	0.98
1989	1.01
1990	1.05
1991	1.08
1992	1.12
1993	1.16
1994	1.2
1995	1.25
1996	1.29
1997	1.34
1998	1.39
1999	1.44
2000	1.49
2001	1.55
2002	1.6
2003	1.66
2004	1.71
2005	1.77
2006	1.83
2007	1.89
2008	1.96
2009	2.02
2010	2.09
2011	2.15
2012	2.22
2013	2.29
2014	2.36
2015	2.44