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	1.04
1980	1.07
1981	1.11
1982	1.14
1983	1.18
1984	1.22
1985	1.26
1986	1.3
1987	1.34
1988	1.39
1989	1.43
1990	1.48
1991	1.53
1992	1.58
1993	1.63
1994	1.69
1995	1.74
1996	1.81
1997	1.87
1998	1.94
1999	2
2000	2.07
2001	2.14
2002	2.22
2003	2.29
2004	2.37
2005	2.45
2006	2.53
2007	2.61
2008	2.69
2009	2.78
2010	2.87
2011	2.96
2012	3.05
2013	3.14
2014	3.23
2015	3.33