Year	Years
1970	1.23
1971	1.26
1972	1.3
1973	1.33
1974	1.36
1975	1.4
1976	1.43
1977	1.46
1978	1.5
1979	1.54
1980	1.57
1981	1.61
1982	1.65
1983	1.69
1984	1.72
1985	1.76
1986	1.8
1987	1.84
1988	1.88
1989	1.92
1990	1.96
1991	2
1992	2.04
1993	2.08
1994	2.12
1995	2.16
1996	2.2
1997	2.24
1998	2.29
1999	2.33
2000	2.38
2001	2.43
2002	2.48
2003	2.54
2004	2.59
2005	2.65
2006	2.71
2007	2.77
2008	2.83
2009	2.89
2010	2.96
2011	3.02
2012	3.09
2013	3.16
2014	3.23
2015	3.3