Year	Years
1970	0.57
1971	0.59
1972	0.61
1973	0.63
1974	0.65
1975	0.68
1976	0.7
1977	0.72
1978	0.75
1979	0.77
1980	0.8
1981	0.82
1982	0.85
1983	0.88
1984	0.91
1985	0.94
1986	0.97
1987	1
1988	1.04
1989	1.07
1990	1.11
1991	1.14
1992	1.18
1993	1.22
1994	1.26
1995	1.3
1996	1.34
1997	1.39
1998	1.43
1999	1.48
2000	1.52
2001	1.57
2002	1.62
2003	1.67
2004	1.73
2005	1.78
2006	1.84
2007	1.89
2008	1.95
2009	2.01
2010	2.07
2011	2.14
2012	2.2
2013	2.27
2014	2.34
2015	2.41