Year	Years
1970	1.39
1971	1.43
1972	1.46
1973	1.5
1974	1.54
1975	1.58
1976	1.62
1977	1.66
1978	1.71
1979	1.75
1980	1.8
1981	1.84
1982	1.89
1983	1.94
1984	1.99
1985	2.04
1986	2.09
1987	2.15
1988	2.2
1989	2.26
1990	2.31
1991	2.37
1992	2.43
1993	2.49
1994	2.56
1995	2.62
1996	2.69
1997	2.76
1998	2.83
1999	2.9
2000	2.97
2001	3.05
2002	3.12
2003	3.2
2004	3.28
2005	3.36
2006	3.44
2007	3.52
2008	3.61
2009	3.69
2010	3.78
2011	3.87
2012	3.96
2013	4.05
2014	4.15
2015	4.24