Year	Years
1970	1.36
1971	1.39
1972	1.43
1973	1.47
1974	1.51
1975	1.55
1976	1.59
1977	1.63
1978	1.67
1979	1.71
1980	1.76
1981	1.8
1982	1.85
1983	1.9
1984	1.95
1985	2
1986	2.05
1987	2.1
1988	2.15
1989	2.21
1990	2.26
1991	2.32
1992	2.38
1993	2.44
1994	2.5
1995	2.56
1996	2.63
1997	2.69
1998	2.76
1999	2.83
2000	2.9
2001	2.97
2002	3.04
2003	3.11
2004	3.19
2005	3.27
2006	3.35
2007	3.43
2008	3.51
2009	3.59
2010	3.68
2011	3.76
2012	3.85
2013	3.94
2014	4.04
2015	4.13