Year	Years
1970	0.5
1971	0.52
1972	0.53
1973	0.55
1974	0.57
1975	0.59
1976	0.61
1977	0.63
1978	0.65
1979	0.67
1980	0.69
1981	0.72
1982	0.74
1983	0.77
1984	0.79
1985	0.82
1986	0.85
1987	0.88
1988	0.91
1989	0.95
1990	0.98
1991	1.02
1992	1.06
1993	1.1
1994	1.14
1995	1.18
1996	1.22
1997	1.27
1998	1.31
1999	1.36
2000	1.4
2001	1.45
2002	1.49
2003	1.54
2004	1.58
2005	1.63
2006	1.68
2007	1.73
2008	1.78
2009	1.83
2010	1.89
2011	1.94
2012	1.99
2013	2.05
2014	2.1
2015	2.16