Year	Years
1970	0.29
1971	0.3
1972	0.31
1973	0.32
1974	0.33
1975	0.35
1976	0.36
1977	0.37
1978	0.39
1979	0.4
1980	0.42
1981	0.44
1982	0.45
1983	0.47
1984	0.49
1985	0.51
1986	0.53
1987	0.55
1988	0.58
1989	0.6
1990	0.63
1991	0.65
1992	0.68
1993	0.71
1994	0.74
1995	0.77
1996	0.8
1997	0.84
1998	0.87
1999	0.91
2000	0.94
2001	0.98
2002	1.02
2003	1.05
2004	1.09
2005	1.13
2006	1.17
2007	1.22
2008	1.26
2009	1.3
2010	1.35
2011	1.39
2012	1.44
2013	1.49
2014	1.53
2015	1.58