Year	Years
1970	0.31
1971	0.32
1972	0.33
1973	0.35
1974	0.36
1975	0.37
1976	0.39
1977	0.4
1978	0.42
1979	0.44
1980	0.45
1981	0.47
1982	0.49
1983	0.51
1984	0.53
1985	0.55
1986	0.58
1987	0.6
1988	0.63
1989	0.65
1990	0.68
1991	0.71
1992	0.74
1993	0.77
1994	0.8
1995	0.83
1996	0.86
1997	0.9
1998	0.93
1999	0.97
2000	1.01
2001	1.04
2002	1.08
2003	1.13
2004	1.17
2005	1.21
2006	1.25
2007	1.3
2008	1.34
2009	1.39
2010	1.43
2011	1.48
2012	1.52
2013	1.56
2014	1.61
2015	1.65