Year	Years
1970	1.91
1971	1.97
1972	2.03
1973	2.09
1974	2.15
1975	2.22
1976	2.29
1977	2.36
1978	2.44
1979	2.51
1980	2.59
1981	2.68
1982	2.77
1983	2.86
1984	2.96
1985	3.06
1986	3.17
1987	3.28
1988	3.4
1989	3.53
1990	3.66
1991	3.81
1992	3.96
1993	4.12
1994	4.3
1995	4.49
1996	4.65
1997	4.81
1998	4.97
1999	5.13
2000	5.29
2001	5.44
2002	5.59
2003	5.75
2004	5.9
2005	6.05
2006	6.2
2007	6.35
2008	6.5
2009	6.65
2010	6.8
2011	6.95
2012	7.1
2013	7.24
2014	7.39
2015	7.54