Year	Years
1970	0.78
1971	0.81
1972	0.83
1973	0.86
1974	0.89
1975	0.92
1976	0.95
1977	0.98
1978	1.02
1979	1.05
1980	1.08
1981	1.12
1982	1.16
1983	1.19
1984	1.23
1985	1.27
1986	1.31
1987	1.35
1988	1.4
1989	1.44
1990	1.49
1991	1.53
1992	1.58
1993	1.63
1994	1.68
1995	1.73
1996	1.77
1997	1.82
1998	1.87
1999	1.92
2000	1.98
2001	2.03
2002	2.09
2003	2.15
2004	2.21
2005	2.27
2006	2.34
2007	2.4
2008	2.47
2009	2.54
2010	2.61
2011	2.68
2012	2.76
2013	2.83
2014	2.91
2015	2.99