Year	Years
1970	1.46
1971	1.49
1972	1.52
1973	1.56
1974	1.59
1975	1.63
1976	1.66
1977	1.7
1978	1.73
1979	1.77
1980	1.8
1981	1.84
1982	1.87
1983	1.91
1984	1.95
1985	1.98
1986	2.02
1987	2.05
1988	2.08
1989	2.12
1990	2.15
1991	2.18
1992	2.21
1993	2.25
1994	2.27
1995	2.3
1996	2.34
1997	2.38
1998	2.43
1999	2.48
2000	2.53
2001	2.58
2002	2.63
2003	2.69
2004	2.74
2005	2.8
2006	2.86
2007	2.93
2008	2.99
2009	3.06
2010	3.12
2011	3.19
2012	3.27
2013	3.34
2014	3.41
2015	3.49