Year	Years
1970	1.38
1971	1.43
1972	1.48
1973	1.53
1974	1.58
1975	1.63
1976	1.69
1977	1.74
1978	1.8
1979	1.87
1980	1.93
1981	1.99
1982	2.06
1983	2.13
1984	2.2
1985	2.28
1986	2.36
1987	2.44
1988	2.52
1989	2.61
1990	2.7
1991	2.79
1992	2.88
1993	2.98
1994	3.08
1995	3.18
1996	3.29
1997	3.41
1998	3.52
1999	3.64
2000	3.75
2001	3.87
2002	4
2003	4.12
2004	4.24
2005	4.37
2006	4.5
2007	4.62
2008	4.75
2009	4.88
2010	5.01
2011	5.15
2012	5.28
2013	5.41
2014	5.55
2015	5.68