Year	Years
1970	1.25
1971	1.29
1972	1.33
1973	1.37
1974	1.42
1975	1.46
1976	1.51
1977	1.56
1978	1.61
1979	1.66
1980	1.71
1981	1.77
1982	1.83
1983	1.88
1984	1.94
1985	2
1986	2.07
1987	2.13
1988	2.2
1989	2.27
1990	2.34
1991	2.41
1992	2.49
1993	2.56
1994	2.64
1995	2.72
1996	2.81
1997	2.89
1998	2.98
1999	3.07
2000	3.16
2001	3.25
2002	3.35
2003	3.45
2004	3.55
2005	3.65
2006	3.75
2007	3.86
2008	3.97
2009	4.08
2010	4.19
2011	4.3
2012	4.42
2013	4.54
2014	4.66
2015	4.78