Year	Years
1970	0.27
1971	0.28
1972	0.29
1973	0.3
1974	0.32
1975	0.33
1976	0.34
1977	0.36
1978	0.37
1979	0.39
1980	0.41
1981	0.42
1982	0.44
1983	0.46
1984	0.48
1985	0.51
1986	0.53
1987	0.55
1988	0.58
1989	0.6
1990	0.63
1991	0.66
1992	0.69
1993	0.73
1994	0.76
1995	0.8
1996	0.84
1997	0.87
1998	0.91
1999	0.95
2000	0.99
2001	1.03
2002	1.07
2003	1.11
2004	1.15
2005	1.2
2006	1.24
2007	1.29
2008	1.33
2009	1.38
2010	1.43
2011	1.48
2012	1.53
2013	1.58
2014	1.64
2015	1.69