Year	Years
1970	0.35
1971	0.37
1972	0.38
1973	0.4
1974	0.41
1975	0.43
1976	0.45
1977	0.46
1978	0.48
1979	0.5
1980	0.52
1981	0.54
1982	0.56
1983	0.59
1984	0.61
1985	0.63
1986	0.66
1987	0.69
1988	0.71
1989	0.74
1990	0.77
1991	0.81
1992	0.84
1993	0.87
1994	0.91
1995	0.94
1996	0.98
1997	1.02
1998	1.06
1999	1.11
2000	1.15
2001	1.19
2002	1.24
2003	1.28
2004	1.33
2005	1.37
2006	1.42
2007	1.47
2008	1.51
2009	1.56
2010	1.61
2011	1.66
2012	1.71
2013	1.76
2014	1.81
2015	1.87