Year	Years
1970	1.93
1971	1.98
1972	2.04
1973	2.09
1974	2.14
1975	2.2
1976	2.26
1977	2.32
1978	2.38
1979	2.44
1980	2.5
1981	2.56
1982	2.63
1983	2.7
1984	2.77
1985	2.84
1986	2.91
1987	2.98
1988	3.06
1989	3.13
1990	3.21
1991	3.29
1992	3.37
1993	3.46
1994	3.54
1995	3.63
1996	3.72
1997	3.81
1998	3.9
1999	3.99
2000	4.09
2001	4.18
2002	4.28
2003	4.38
2004	4.48
2005	4.58
2006	4.68
2007	4.79
2008	4.89
2009	5
2010	5.11
2011	5.21
2012	5.33
2013	5.44
2014	5.55
2015	5.66