Year	Years
1970	0.32
1971	0.34
1972	0.35
1973	0.36
1974	0.37
1975	0.39
1976	0.4
1977	0.41
1978	0.43
1979	0.45
1980	0.46
1981	0.48
1982	0.5
1983	0.51
1984	0.53
1985	0.55
1986	0.57
1987	0.59
1988	0.62
1989	0.64
1990	0.66
1991	0.69
1992	0.71
1993	0.74
1994	0.77
1995	0.8
1996	0.83
1997	0.86
1998	0.89
1999	0.92
2000	0.95
2001	0.98
2002	1.02
2003	1.05
2004	1.09
2005	1.13
2006	1.16
2007	1.2
2008	1.24
2009	1.29
2010	1.33
2011	1.37
2012	1.42
2013	1.46
2014	1.51
2015	1.56