Year	Years
1970	1.33
1971	1.36
1972	1.4
1973	1.44
1974	1.48
1975	1.52
1976	1.56
1977	1.6
1978	1.65
1979	1.7
1980	1.74
1981	1.79
1982	1.84
1983	1.89
1984	1.94
1985	2
1986	2.05
1987	2.11
1988	2.17
1989	2.23
1990	2.29
1991	2.35
1992	2.42
1993	2.49
1994	2.56
1995	2.63
1996	2.7
1997	2.78
1998	2.86
1999	2.93
2000	3.01
2001	3.09
2002	3.17
2003	3.25
2004	3.34
2005	3.42
2006	3.51
2007	3.59
2008	3.68
2009	3.77
2010	3.86
2011	3.95
2012	4.05
2013	4.14
2014	4.24
2015	4.34