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	0.82
1983	0.85
1984	0.89
1985	0.92
1986	0.96
1987	1
1988	1.05
1989	1.09
1990	1.14
1991	1.19
1992	1.24
1993	1.3
1994	1.36
1995	1.42
1996	1.48
1997	1.54
1998	1.6
1999	1.66
2000	1.72
2001	1.78
2002	1.84
2003	1.91
2004	1.98
2005	2.04
2006	2.11
2007	2.18
2008	2.26
2009	2.33
2010	2.4
2011	2.48
2012	2.56
2013	2.64
2014	2.72
2015	2.8