Year	Years
1970	0.66
1971	0.69
1972	0.71
1973	0.73
1974	0.76
1975	0.78
1976	0.81
1977	0.84
1978	0.87
1979	0.89
1980	0.92
1981	0.96
1982	0.99
1983	1.02
1984	1.05
1985	1.09
1986	1.13
1987	1.16
1988	1.2
1989	1.24
1990	1.28
1991	1.33
1992	1.37
1993	1.42
1994	1.46
1995	1.51
1996	1.56
1997	1.61
1998	1.66
1999	1.72
2000	1.77
2001	1.83
2002	1.89
2003	1.94
2004	2.01
2005	2.07
2006	2.13
2007	2.2
2008	2.27
2009	2.34
2010	2.41
2011	2.48
2012	2.56
2013	2.63
2014	2.71
2015	2.79