Year	Years
1970	0.77
1971	0.8
1972	0.82
1973	0.85
1974	0.88
1975	0.91
1976	0.94
1977	0.97
1978	1
1979	1.03
1980	1.07
1981	1.1
1982	1.14
1983	1.18
1984	1.21
1985	1.25
1986	1.29
1987	1.34
1988	1.38
1989	1.42
1990	1.47
1991	1.52
1992	1.56
1993	1.61
1994	1.67
1995	1.72
1996	1.77
1997	1.83
1998	1.88
1999	1.94
2000	2
2001	2.06
2002	2.13
2003	2.19
2004	2.26
2005	2.33
2006	2.4
2007	2.47
2008	2.54
2009	2.62
2010	2.7
2011	2.78
2012	2.86
2013	2.94
2014	3.03
2015	3.12