Year	Years
1970	1.19
1971	1.22
1972	1.26
1973	1.3
1974	1.34
1975	1.38
1976	1.41
1977	1.46
1978	1.5
1979	1.54
1980	1.58
1981	1.62
1982	1.66
1983	1.71
1984	1.75
1985	1.79
1986	1.83
1987	1.87
1988	1.92
1989	1.96
1990	2
1991	2.04
1992	2.08
1993	2.11
1994	2.15
1995	2.19
1996	2.22
1997	2.25
1998	2.29
1999	2.33
2000	2.38
2001	2.42
2002	2.47
2003	2.52
2004	2.58
2005	2.63
2006	2.69
2007	2.75
2008	2.81
2009	2.88
2010	2.94
2011	3.01
2012	3.08
2013	3.16
2014	3.23
2015	3.31