Year	Years
1970	0.74
1971	0.76
1972	0.79
1973	0.81
1974	0.83
1975	0.86
1976	0.88
1977	0.91
1978	0.94
1979	0.97
1980	0.99
1981	1.02
1982	1.06
1983	1.09
1984	1.12
1985	1.15
1986	1.19
1987	1.23
1988	1.26
1989	1.3
1990	1.34
1991	1.38
1992	1.43
1993	1.47
1994	1.52
1995	1.56
1996	1.61
1997	1.65
1998	1.7
1999	1.75
2000	1.79
2001	1.84
2002	1.89
2003	1.94
2004	1.99
2005	2.04
2006	2.1
2007	2.15
2008	2.21
2009	2.26
2010	2.32
2011	2.38
2012	2.44
2013	2.5
2014	2.56
2015	2.63