Year	Years
1970	0.43
1971	0.44
1972	0.46
1973	0.48
1974	0.5
1975	0.52
1976	0.53
1977	0.55
1978	0.58
1979	0.6
1980	0.62
1981	0.64
1982	0.67
1983	0.69
1984	0.72
1985	0.75
1986	0.78
1987	0.81
1988	0.84
1989	0.87
1990	0.9
1991	0.94
1992	0.97
1993	1.01
1994	1.05
1995	1.09
1996	1.12
1997	1.16
1998	1.2
1999	1.24
2000	1.28
2001	1.32
2002	1.36
2003	1.41
2004	1.45
2005	1.5
2006	1.55
2007	1.6
2008	1.65
2009	1.7
2010	1.75
2011	1.81
2012	1.87
2013	1.92
2014	1.98
2015	2.04