Year	Years
1970	0.25
1971	0.26
1972	0.27
1973	0.28
1974	0.29
1975	0.3
1976	0.31
1977	0.32
1978	0.34
1979	0.35
1980	0.37
1981	0.38
1982	0.4
1983	0.42
1984	0.43
1985	0.45
1986	0.47
1987	0.5
1988	0.52
1989	0.54
1990	0.57
1991	0.6
1992	0.63
1993	0.66
1994	0.69
1995	0.72
1996	0.76
1997	0.8
1998	0.84
1999	0.89
2000	0.93
2001	0.98
2002	1.02
2003	1.07
2004	1.12
2005	1.17
2006	1.22
2007	1.27
2008	1.32
2009	1.37
2010	1.42
2011	1.47
2012	1.52
2013	1.57
2014	1.63
2015	1.68