Year	Years
1970	0.47
1971	0.49
1972	0.5
1973	0.52
1974	0.54
1975	0.56
1976	0.57
1977	0.59
1978	0.61
1979	0.63
1980	0.66
1981	0.68
1982	0.7
1983	0.72
1984	0.75
1985	0.77
1986	0.8
1987	0.82
1988	0.85
1989	0.88
1990	0.91
1991	0.94
1992	0.97
1993	1
1994	1.03
1995	1.06
1996	1.1
1997	1.13
1998	1.17
1999	1.21
2000	1.25
2001	1.29
2002	1.33
2003	1.37
2004	1.41
2005	1.46
2006	1.5
2007	1.55
2008	1.6
2009	1.65
2010	1.7
2011	1.75
2012	1.81
2013	1.87
2014	1.92
2015	1.98