Year	Years
1970	1.74
1971	1.79
1972	1.85
1973	1.9
1974	1.96
1975	2.02
1976	2.09
1977	2.15
1978	2.22
1979	2.28
1980	2.35
1981	2.43
1982	2.5
1983	2.57
1984	2.65
1985	2.73
1986	2.81
1987	2.9
1988	2.98
1989	3.07
1990	3.16
1991	3.25
1992	3.35
1993	3.44
1994	3.54
1995	3.65
1996	3.75
1997	3.86
1998	3.97
1999	4.08
2000	4.19
2001	4.3
2002	4.42
2003	4.54
2004	4.66
2005	4.79
2006	4.91
2007	5.04
2008	5.17
2009	5.3
2010	5.44
2011	5.57
2012	5.71
2013	5.85
2014	5.99
2015	6.13