Year	Years
1970	0.73
1971	0.75
1972	0.78
1973	0.8
1974	0.83
1975	0.86
1976	0.89
1977	0.92
1978	0.95
1979	0.98
1980	1.01
1981	1.05
1982	1.08
1983	1.12
1984	1.15
1985	1.19
1986	1.23
1987	1.27
1988	1.32
1989	1.36
1990	1.4
1991	1.45
1992	1.5
1993	1.55
1994	1.6
1995	1.65
1996	1.7
1997	1.76
1998	1.81
1999	1.87
2000	1.93
2001	1.99
2002	2.05
2003	2.12
2004	2.18
2005	2.25
2006	2.32
2007	2.39
2008	2.46
2009	2.53
2010	2.61
2011	2.68
2012	2.76
2013	2.84
2014	2.93
2015	3.01