Year	Years
1970	1.98
1971	2.06
1972	2.15
1973	2.24
1974	2.33
1975	2.43
1976	2.54
1977	2.65
1978	2.76
1979	2.88
1980	3.01
1981	3.14
1982	3.28
1983	3.42
1984	3.58
1985	3.74
1986	3.91
1987	4.09
1988	4.27
1989	4.47
1990	4.68
1991	4.9
1992	5.13
1993	5.38
1994	5.63
1995	5.9
1996	6.09
1997	6.28
1998	6.47
1999	6.65
2000	6.83
2001	7.01
2002	7.19
2003	7.37
2004	7.54
2005	7.72
2006	7.89
2007	8.06
2008	8.23
2009	8.39
2010	8.56
2011	8.73
2012	8.89
2013	9.06
2014	9.22
2015	9.38