Year	Years
1970	0.46
1971	0.48
1972	0.5
1973	0.51
1974	0.53
1975	0.55
1976	0.57
1977	0.59
1978	0.61
1979	0.63
1980	0.65
1981	0.67
1982	0.69
1983	0.72
1984	0.74
1985	0.77
1986	0.79
1987	0.82
1988	0.85
1989	0.88
1990	0.91
1991	0.94
1992	0.97
1993	1
1994	1.04
1995	1.07
1996	1.11
1997	1.14
1998	1.18
1999	1.22
2000	1.26
2001	1.3
2002	1.34
2003	1.39
2004	1.43
2005	1.48
2006	1.52
2007	1.57
2008	1.62
2009	1.67
2010	1.73
2011	1.78
2012	1.84
2013	1.89
2014	1.95
2015	2.01