Year	Years
1970	1.47
1971	1.52
1972	1.58
1973	1.64
1974	1.7
1975	1.76
1976	1.83
1977	1.89
1978	1.96
1979	2.03
1980	2.11
1981	2.18
1982	2.26
1983	2.34
1984	2.43
1985	2.51
1986	2.6
1987	2.7
1988	2.79
1989	2.89
1990	2.99
1991	3.09
1992	3.19
1993	3.3
1994	3.4
1995	3.51
1996	3.63
1997	3.74
1998	3.85
1999	3.97
2000	4.08
2001	4.2
2002	4.31
2003	4.43
2004	4.54
2005	4.66
2006	4.77
2007	4.88
2008	4.99
2009	5.11
2010	5.22
2011	5.33
2012	5.44
2013	5.56
2014	5.67
2015	5.79