Year	Years
1970	0.64
1971	0.66
1972	0.68
1973	0.7
1974	0.72
1975	0.74
1976	0.76
1977	0.78
1978	0.8
1979	0.82
1980	0.85
1981	0.87
1982	0.9
1983	0.92
1984	0.95
1985	0.97
1986	1
1987	1.03
1988	1.06
1989	1.09
1990	1.12
1991	1.15
1992	1.18
1993	1.21
1994	1.25
1995	1.28
1996	1.32
1997	1.36
1998	1.39
1999	1.43
2000	1.47
2001	1.51
2002	1.55
2003	1.6
2004	1.64
2005	1.68
2006	1.73
2007	1.77
2008	1.82
2009	1.87
2010	1.92
2011	1.97
2012	2.02
2013	2.07
2014	2.12
2015	2.18