Year	Years
1970	1.84
1971	1.9
1972	1.96
1973	2.02
1974	2.08
1975	2.14
1976	2.21
1977	2.28
1978	2.34
1979	2.42
1980	2.49
1981	2.56
1982	2.64
1983	2.72
1984	2.8
1985	2.88
1986	2.96
1987	3.05
1988	3.14
1989	3.23
1990	3.32
1991	3.41
1992	3.51
1993	3.61
1994	3.71
1995	3.81
1996	3.91
1997	4.02
1998	4.12
1999	4.23
2000	4.34
2001	4.45
2002	4.57
2003	4.69
2004	4.81
2005	4.93
2006	5.05
2007	5.18
2008	5.3
2009	5.43
2010	5.57
2011	5.7
2012	5.84
2013	5.97
2014	6.12
2015	6.26