Year	Years
1970	0.39
1971	0.41
1972	0.42
1973	0.44
1974	0.46
1975	0.47
1976	0.49
1977	0.51
1978	0.53
1979	0.55
1980	0.57
1981	0.59
1982	0.62
1983	0.64
1984	0.67
1985	0.69
1986	0.72
1987	0.75
1988	0.78
1989	0.81
1990	0.84
1991	0.88
1992	0.91
1993	0.95
1994	0.99
1995	1.03
1996	1.07
1997	1.11
1998	1.16
1999	1.2
2000	1.25
2001	1.29
2002	1.34
2003	1.39
2004	1.44
2005	1.49
2006	1.54
2007	1.59
2008	1.65
2009	1.7
2010	1.75
2011	1.81
2012	1.86
2013	1.92
2014	1.98
2015	2.04