Year	Years
1970	2.95
1971	3.02
1972	3.09
1973	3.17
1974	3.24
1975	3.32
1976	3.4
1977	3.48
1978	3.56
1979	3.65
1980	3.73
1981	3.82
1982	3.91
1983	4
1984	4.09
1985	4.18
1986	4.27
1987	4.37
1988	4.47
1989	4.56
1990	4.66
1991	4.77
1992	4.87
1993	4.97
1994	5.08
1995	5.19
1996	5.3
1997	5.41
1998	5.52
1999	5.64
2000	5.75
2001	5.87
2002	5.99
2003	6.11
2004	6.23
2005	6.36
2006	6.48
2007	6.6
2008	6.73
2009	6.86
2010	6.99
2011	7.11
2012	7.24
2013	7.37
2014	7.5
2015	7.63