Year	Years
1970	1.29
1971	1.33
1972	1.37
1973	1.42
1974	1.46
1975	1.51
1976	1.56
1977	1.61
1978	1.66
1979	1.71
1980	1.77
1981	1.82
1982	1.88
1983	1.94
1984	2
1985	2.07
1986	2.13
1987	2.2
1988	2.27
1989	2.34
1990	2.41
1991	2.48
1992	2.56
1993	2.64
1994	2.72
1995	2.81
1996	2.89
1997	2.98
1998	3.07
1999	3.16
2000	3.26
2001	3.35
2002	3.45
2003	3.55
2004	3.65
2005	3.75
2006	3.86
2007	3.97
2008	4.08
2009	4.19
2010	4.31
2011	4.42
2012	4.54
2013	4.66
2014	4.79
2015	4.91