Year	Years
1970	1.93
1971	1.99
1972	2.05
1973	2.11
1974	2.17
1975	2.24
1976	2.31
1977	2.37
1978	2.45
1979	2.52
1980	2.59
1981	2.67
1982	2.75
1983	2.83
1984	2.91
1985	2.99
1986	3.08
1987	3.17
1988	3.26
1989	3.35
1990	3.44
1991	3.54
1992	3.64
1993	3.74
1994	3.84
1995	3.95
1996	4.06
1997	4.17
1998	4.28
1999	4.39
2000	4.51
2001	4.63
2002	4.75
2003	4.87
2004	5
2005	5.12
2006	5.25
2007	5.38
2008	5.52
2009	5.65
2010	5.79
2011	5.93
2012	6.07
2013	6.22
2014	6.36
2015	6.51