Year	Years
1970	0.5
1971	0.51
1972	0.53
1973	0.54
1974	0.56
1975	0.57
1976	0.59
1977	0.6
1978	0.62
1979	0.64
1980	0.65
1981	0.67
1982	0.69
1983	0.71
1984	0.73
1985	0.75
1986	0.77
1987	0.79
1988	0.81
1989	0.83
1990	0.86
1991	0.88
1992	0.9
1993	0.93
1994	0.95
1995	0.98
1996	1.01
1997	1.03
1998	1.06
1999	1.09
2000	1.12
2001	1.15
2002	1.18
2003	1.21
2004	1.24
2005	1.28
2006	1.31
2007	1.35
2008	1.38
2009	1.42
2010	1.46
2011	1.5
2012	1.53
2013	1.58
2014	1.62
2015	1.66