Year	Years
1970	0.36
1971	0.37
1972	0.38
1973	0.39
1974	0.41
1975	0.42
1976	0.43
1977	0.45
1978	0.47
1979	0.48
1980	0.5
1981	0.52
1982	0.54
1983	0.55
1984	0.58
1985	0.6
1986	0.62
1987	0.64
1988	0.67
1989	0.7
1990	0.72
1991	0.75
1992	0.78
1993	0.82
1994	0.85
1995	0.89
1996	0.93
1997	0.98
1998	1.02
1999	1.06
2000	1.1
2001	1.15
2002	1.19
2003	1.24
2004	1.28
2005	1.33
2006	1.38
2007	1.43
2008	1.47
2009	1.52
2010	1.57
2011	1.62
2012	1.67
2013	1.73
2014	1.78
2015	1.83