Year	Years
1970	1.25
1971	1.27
1972	1.3
1973	1.33
1974	1.36
1975	1.39
1976	1.41
1977	1.44
1978	1.47
1979	1.5
1980	1.53
1981	1.56
1982	1.59
1983	1.62
1984	1.65
1985	1.68
1986	1.71
1987	1.73
1988	1.76
1989	1.79
1990	1.82
1991	1.85
1992	1.88
1993	1.91
1994	1.94
1995	1.97
1996	2.01
1997	2.06
1998	2.11
1999	2.16
2000	2.21
2001	2.26
2002	2.32
2003	2.37
2004	2.43
2005	2.49
2006	2.55
2007	2.61
2008	2.67
2009	2.74
2010	2.8
2011	2.87
2012	2.94
2013	3.01
2014	3.08
2015	3.16