Year	Years
1970	0.58
1971	0.6
1972	0.62
1973	0.65
1974	0.67
1975	0.7
1976	0.73
1977	0.76
1978	0.79
1979	0.82
1980	0.86
1981	0.89
1982	0.93
1983	0.97
1984	1.01
1985	1.05
1986	1.1
1987	1.15
1988	1.2
1989	1.25
1990	1.3
1991	1.36
1992	1.42
1993	1.49
1994	1.55
1995	1.62
1996	1.69
1997	1.76
1998	1.82
1999	1.89
2000	1.96
2001	2.03
2002	2.11
2003	2.18
2004	2.25
2005	2.33
2006	2.41
2007	2.48
2008	2.56
2009	2.64
2010	2.72
2011	2.81
2012	2.89
2013	2.98
2014	3.06
2015	3.15