Year	Years
1970	1.44
1971	1.48
1972	1.53
1973	1.58
1974	1.62
1975	1.68
1976	1.73
1977	1.78
1978	1.84
1979	1.89
1980	1.95
1981	2.01
1982	2.07
1983	2.13
1984	2.2
1985	2.26
1986	2.33
1987	2.4
1988	2.47
1989	2.54
1990	2.62
1991	2.69
1992	2.77
1993	2.85
1994	2.93
1995	3.02
1996	3.1
1997	3.19
1998	3.28
1999	3.38
2000	3.47
2001	3.57
2002	3.67
2003	3.77
2004	3.88
2005	3.98
2006	4.09
2007	4.2
2008	4.31
2009	4.43
2010	4.55
2011	4.66
2012	4.79
2013	4.91
2014	5.04
2015	5.16