Year	Years
1970	1.14
1971	1.18
1972	1.21
1973	1.24
1974	1.28
1975	1.31
1976	1.35
1977	1.39
1978	1.43
1979	1.47
1980	1.51
1981	1.55
1982	1.6
1983	1.64
1984	1.69
1985	1.74
1986	1.78
1987	1.84
1988	1.89
1989	1.94
1990	2
1991	2.05
1992	2.11
1993	2.17
1994	2.23
1995	2.3
1996	2.37
1997	2.44
1998	2.51
1999	2.58
2000	2.65
2001	2.73
2002	2.8
2003	2.88
2004	2.96
2005	3.04
2006	3.12
2007	3.2
2008	3.28
2009	3.37
2010	3.45
2011	3.54
2012	3.62
2013	3.71
2014	3.8
2015	3.89