Year	Years
1970	1.32
1971	1.37
1972	1.42
1973	1.47
1974	1.53
1975	1.58
1976	1.64
1977	1.69
1978	1.75
1979	1.81
1980	1.88
1981	1.94
1982	2.01
1983	2.07
1984	2.14
1985	2.21
1986	2.28
1987	2.36
1988	2.43
1989	2.5
1990	2.58
1991	2.65
1992	2.72
1993	2.8
1994	2.87
1995	2.94
1996	3.01
1997	3.08
1998	3.14
1999	3.21
2000	3.28
2001	3.35
2002	3.42
2003	3.49
2004	3.56
2005	3.64
2006	3.71
2007	3.79
2008	3.87
2009	3.95
2010	4.04
2011	4.13
2012	4.22
2013	4.31
2014	4.4
2015	4.5