Year	Years
1970	0.58
1971	0.59
1972	0.61
1973	0.63
1974	0.65
1975	0.67
1976	0.69
1977	0.71
1978	0.73
1979	0.75
1980	0.77
1981	0.8
1982	0.82
1983	0.85
1984	0.87
1985	0.9
1986	0.93
1987	0.95
1988	0.98
1989	1.02
1990	1.05
1991	1.08
1992	1.11
1993	1.15
1994	1.19
1995	1.22
1996	1.27
1997	1.31
1998	1.35
1999	1.39
2000	1.44
2001	1.48
2002	1.52
2003	1.57
2004	1.62
2005	1.66
2006	1.71
2007	1.76
2008	1.81
2009	1.86
2010	1.91
2011	1.97
2012	2.02
2013	2.08
2014	2.13
2015	2.19