Year	Years
1970	1.48
1971	1.53
1972	1.58
1973	1.63
1974	1.68
1975	1.73
1976	1.78
1977	1.84
1978	1.9
1979	1.95
1980	2.01
1981	2.07
1982	2.14
1983	2.2
1984	2.27
1985	2.33
1986	2.4
1987	2.47
1988	2.55
1989	2.62
1990	2.7
1991	2.78
1992	2.86
1993	2.94
1994	3.03
1995	3.11
1996	3.21
1997	3.3
1998	3.4
1999	3.5
2000	3.6
2001	3.7
2002	3.81
2003	3.91
2004	4.02
2005	4.13
2006	4.25
2007	4.36
2008	4.48
2009	4.6
2010	4.72
2011	4.85
2012	4.97
2013	5.1
2014	5.23
2015	5.36