Year	Years
1970	0.31
1971	0.32
1972	0.33
1973	0.34
1974	0.36
1975	0.37
1976	0.38
1977	0.39
1978	0.41
1979	0.42
1980	0.43
1981	0.45
1982	0.46
1983	0.48
1984	0.49
1985	0.51
1986	0.53
1987	0.54
1988	0.56
1989	0.58
1990	0.6
1991	0.62
1992	0.64
1993	0.66
1994	0.68
1995	0.7
1996	0.73
1997	0.76
1998	0.78
1999	0.81
2000	0.84
2001	0.87
2002	0.9
2003	0.93
2004	0.96
2005	0.99
2006	1.03
2007	1.06
2008	1.1
2009	1.13
2010	1.17
2011	1.21
2012	1.25
2013	1.29
2014	1.33
2015	1.38