Year	Years
1970	0.68
1971	0.71
1972	0.73
1973	0.76
1974	0.78
1975	0.81
1976	0.84
1977	0.87
1978	0.9
1979	0.94
1980	0.97
1981	1.01
1982	1.04
1983	1.08
1984	1.12
1985	1.16
1986	1.21
1987	1.25
1988	1.3
1989	1.35
1990	1.4
1991	1.45
1992	1.5
1993	1.56
1994	1.62
1995	1.68
1996	1.75
1997	1.82
1998	1.89
1999	1.96
2000	2.04
2001	2.11
2002	2.19
2003	2.27
2004	2.35
2005	2.43
2006	2.52
2007	2.6
2008	2.69
2009	2.78
2010	2.87
2011	2.95
2012	3.05
2013	3.14
2014	3.23
2015	3.32