Year	Years
1970	0.98
1971	1
1972	1.03
1973	1.06
1974	1.09
1975	1.12
1976	1.15
1977	1.18
1978	1.21
1979	1.25
1980	1.28
1981	1.32
1982	1.35
1983	1.39
1984	1.43
1985	1.47
1986	1.51
1987	1.55
1988	1.59
1989	1.63
1990	1.68
1991	1.72
1992	1.77
1993	1.82
1994	1.86
1995	1.91
1996	1.97
1997	2.02
1998	2.07
1999	2.13
2000	2.18
2001	2.24
2002	2.3
2003	2.36
2004	2.42
2005	2.48
2006	2.54
2007	2.6
2008	2.67
2009	2.73
2010	2.8
2011	2.87
2012	2.94
2013	3.01
2014	3.08
2015	3.15