Year	Years
1970	1.16
1971	1.19
1972	1.23
1973	1.26
1974	1.29
1975	1.33
1976	1.36
1977	1.4
1978	1.43
1979	1.47
1980	1.51
1981	1.55
1982	1.59
1983	1.63
1984	1.67
1985	1.72
1986	1.76
1987	1.81
1988	1.85
1989	1.9
1990	1.95
1991	2
1992	2.05
1993	2.1
1994	2.16
1995	2.21
1996	2.27
1997	2.33
1998	2.38
1999	2.44
2000	2.5
2001	2.56
2002	2.63
2003	2.69
2004	2.76
2005	2.83
2006	2.89
2007	2.97
2008	3.04
2009	3.11
2010	3.19
2011	3.26
2012	3.34
2013	3.42
2014	3.51
2015	3.59