Year	Years
1970	1.49
1971	1.54
1972	1.59
1973	1.64
1974	1.7
1975	1.75
1976	1.81
1977	1.87
1978	1.93
1979	1.99
1980	2.06
1981	2.12
1982	2.19
1983	2.26
1984	2.33
1985	2.41
1986	2.49
1987	2.56
1988	2.65
1989	2.73
1990	2.82
1991	2.91
1992	3
1993	3.09
1994	3.19
1995	3.28
1996	3.39
1997	3.49
1998	3.59
1999	3.7
2000	3.81
2001	3.92
2002	4.03
2003	4.15
2004	4.26
2005	4.38
2006	4.5
2007	4.62
2008	4.74
2009	4.87
2010	4.99
2011	5.12
2012	5.25
2013	5.38
2014	5.51
2015	5.65