Year	Years
1970	1.59
1971	1.64
1972	1.69
1973	1.75
1974	1.8
1975	1.86
1976	1.91
1977	1.97
1978	2.03
1979	2.1
1980	2.16
1981	2.23
1982	2.29
1983	2.36
1984	2.43
1985	2.51
1986	2.58
1987	2.66
1988	2.74
1989	2.82
1990	2.9
1991	2.99
1992	3.08
1993	3.17
1994	3.26
1995	3.36
1996	3.46
1997	3.57
1998	3.67
1999	3.78
2000	3.9
2001	4.01
2002	4.13
2003	4.25
2004	4.37
2005	4.49
2006	4.62
2007	4.75
2008	4.88
2009	5.01
2010	5.14
2011	5.28
2012	5.42
2013	5.56
2014	5.7
2015	5.84