Year	Years
1970	1.75
1971	1.82
1972	1.88
1973	1.95
1974	2.02
1975	2.09
1976	2.17
1977	2.25
1978	2.33
1979	2.41
1980	2.5
1981	2.58
1982	2.67
1983	2.77
1984	2.86
1985	2.96
1986	3.06
1987	3.16
1988	3.27
1989	3.37
1990	3.48
1991	3.59
1992	3.7
1993	3.81
1994	3.92
1995	4.04
1996	4.14
1997	4.25
1998	4.36
1999	4.47
2000	4.57
2001	4.68
2002	4.79
2003	4.89
2004	5
2005	5.11
2006	5.22
2007	5.33
2008	5.44
2009	5.55
2010	5.67
2011	5.78
2012	5.9
2013	6.02
2014	6.14
2015	6.26