Year	Years
1970	0.71
1971	0.74
1972	0.77
1973	0.79
1974	0.83
1975	0.86
1976	0.89
1977	0.93
1978	0.96
1979	1
1980	1.04
1981	1.08
1982	1.13
1983	1.17
1984	1.22
1985	1.28
1986	1.33
1987	1.39
1988	1.45
1989	1.52
1990	1.59
1991	1.67
1992	1.75
1993	1.84
1994	1.94
1995	2.05
1996	2.14
1997	2.24
1998	2.34
1999	2.44
2000	2.53
2001	2.64
2002	2.74
2003	2.84
2004	2.94
2005	3.05
2006	3.16
2007	3.27
2008	3.38
2009	3.49
2010	3.6
2011	3.72
2012	3.83
2013	3.95
2014	4.07
2015	4.19