Year	Years
1970	1.51
1971	1.58
1972	1.65
1973	1.73
1974	1.81
1975	1.9
1976	1.99
1977	2.09
1978	2.19
1979	2.3
1980	2.41
1981	2.53
1982	2.66
1983	2.8
1984	2.94
1985	3.1
1986	3.27
1987	3.44
1988	3.63
1989	3.83
1990	4.04
1991	4.26
1992	4.5
1993	4.74
1994	5.01
1995	5.28
1996	5.49
1997	5.69
1998	5.9
1999	6.1
2000	6.3
2001	6.5
2002	6.7
2003	6.89
2004	7.08
2005	7.28
2006	7.47
2007	7.65
2008	7.84
2009	8.03
2010	8.21
2011	8.39
2012	8.57
2013	8.75
2014	8.93
2015	9.1