Year	Years
1970	1.65
1971	1.69
1972	1.74
1973	1.79
1974	1.83
1975	1.88
1976	1.93
1977	1.98
1978	2.04
1979	2.09
1980	2.15
1981	2.2
1982	2.26
1983	2.32
1984	2.38
1985	2.44
1986	2.51
1987	2.57
1988	2.64
1989	2.71
1990	2.78
1991	2.85
1992	2.93
1993	3.01
1994	3.08
1995	3.16
1996	3.25
1997	3.34
1998	3.43
1999	3.51
2000	3.61
2001	3.7
2002	3.79
2003	3.89
2004	3.98
2005	4.08
2006	4.18
2007	4.28
2008	4.38
2009	4.48
2010	4.58
2011	4.69
2012	4.79
2013	4.9
2014	5.01
2015	5.12