Year	Years
1970	1.33
1971	1.37
1972	1.4
1973	1.44
1974	1.48
1975	1.52
1976	1.56
1977	1.6
1978	1.65
1979	1.69
1980	1.74
1981	1.78
1982	1.83
1983	1.88
1984	1.93
1985	1.98
1986	2.03
1987	2.09
1988	2.14
1989	2.2
1990	2.26
1991	2.32
1992	2.38
1993	2.44
1994	2.51
1995	2.57
1996	2.64
1997	2.71
1998	2.78
1999	2.85
2000	2.93
2001	3
2002	3.08
2003	3.15
2004	3.23
2005	3.31
2006	3.39
2007	3.47
2008	3.56
2009	3.64
2010	3.73
2011	3.82
2012	3.9
2013	3.99
2014	4.09
2015	4.18