Year	Years
1970	0.93
1971	0.96
1972	0.98
1973	1.01
1974	1.04
1975	1.07
1976	1.1
1977	1.13
1978	1.16
1979	1.19
1980	1.22
1981	1.26
1982	1.29
1983	1.33
1984	1.36
1985	1.4
1986	1.44
1987	1.48
1988	1.52
1989	1.56
1990	1.61
1991	1.65
1992	1.7
1993	1.74
1994	1.79
1995	1.84
1996	1.89
1997	1.95
1998	2
1999	2.06
2000	2.11
2001	2.17
2002	2.23
2003	2.29
2004	2.35
2005	2.41
2006	2.47
2007	2.54
2008	2.6
2009	2.67
2010	2.74
2011	2.81
2012	2.88
2013	2.95
2014	3.02
2015	3.09