Year	Years
1970	1.81
1971	1.87
1972	1.93
1973	1.99
1974	2.05
1975	2.12
1976	2.19
1977	2.26
1978	2.33
1979	2.41
1980	2.48
1981	2.56
1982	2.64
1983	2.73
1984	2.81
1985	2.9
1986	2.99
1987	3.08
1988	3.18
1989	3.28
1990	3.38
1991	3.48
1992	3.58
1993	3.69
1994	3.8
1995	3.91
1996	4.03
1997	4.14
1998	4.26
1999	4.39
2000	4.51
2001	4.64
2002	4.77
2003	4.9
2004	5.03
2005	5.16
2006	5.29
2007	5.43
2008	5.57
2009	5.7
2010	5.84
2011	5.99
2012	6.13
2013	6.27
2014	6.41
2015	6.56