Year	Years
1970	0.56
1971	0.58
1972	0.6
1973	0.61
1974	0.63
1975	0.65
1976	0.67
1977	0.69
1978	0.71
1979	0.73
1980	0.75
1981	0.77
1982	0.79
1983	0.81
1984	0.84
1985	0.86
1986	0.89
1987	0.91
1988	0.94
1989	0.97
1990	1
1991	1.03
1992	1.06
1993	1.09
1994	1.12
1995	1.16
1996	1.19
1997	1.23
1998	1.27
1999	1.31
2000	1.35
2001	1.39
2002	1.43
2003	1.48
2004	1.52
2005	1.57
2006	1.61
2007	1.66
2008	1.71
2009	1.75
2010	1.8
2011	1.85
2012	1.9
2013	1.96
2014	2.01
2015	2.06