Year	Years
1970	2.03
1971	2.09
1972	2.15
1973	2.22
1974	2.29
1975	2.36
1976	2.43
1977	2.5
1978	2.57
1979	2.65
1980	2.73
1981	2.81
1982	2.89
1983	2.98
1984	3.06
1985	3.15
1986	3.24
1987	3.33
1988	3.43
1989	3.52
1990	3.62
1991	3.72
1992	3.82
1993	3.92
1994	4.02
1995	4.13
1996	4.24
1997	4.35
1998	4.46
1999	4.58
2000	4.69
2001	4.81
2002	4.93
2003	5.06
2004	5.18
2005	5.31
2006	5.44
2007	5.57
2008	5.71
2009	5.84
2010	5.98
2011	6.12
2012	6.26
2013	6.41
2014	6.55
2015	6.7