Year	Years
1970	1.17
1971	1.21
1972	1.25
1973	1.29
1974	1.34
1975	1.38
1976	1.43
1977	1.48
1978	1.53
1979	1.58
1980	1.63
1981	1.69
1982	1.75
1983	1.81
1984	1.87
1985	1.93
1986	2
1987	2.07
1988	2.14
1989	2.21
1990	2.28
1991	2.36
1992	2.44
1993	2.53
1994	2.61
1995	2.7
1996	2.79
1997	2.88
1998	2.97
1999	3.07
2000	3.16
2001	3.26
2002	3.36
2003	3.46
2004	3.57
2005	3.67
2006	3.78
2007	3.89
2008	4
2009	4.11
2010	4.23
2011	4.35
2012	4.47
2013	4.59
2014	4.71
2015	4.84