Year	Years
1970	0.47
1971	0.48
1972	0.5
1973	0.52
1974	0.53
1975	0.55
1976	0.57
1977	0.59
1978	0.61
1979	0.63
1980	0.65
1981	0.67
1982	0.7
1983	0.72
1984	0.74
1985	0.77
1986	0.8
1987	0.82
1988	0.85
1989	0.88
1990	0.91
1991	0.94
1992	0.97
1993	1.01
1994	1.04
1995	1.08
1996	1.11
1997	1.15
1998	1.19
1999	1.23
2000	1.27
2001	1.32
2002	1.36
2003	1.41
2004	1.46
2005	1.5
2006	1.55
2007	1.6
2008	1.66
2009	1.71
2010	1.77
2011	1.82
2012	1.88
2013	1.94
2014	2
2015	2.07