Year	Years
1970	1.25
1971	1.29
1972	1.34
1973	1.38
1974	1.43
1975	1.48
1976	1.53
1977	1.59
1978	1.64
1979	1.7
1980	1.76
1981	1.82
1982	1.89
1983	1.95
1984	2.02
1985	2.09
1986	2.17
1987	2.24
1988	2.32
1989	2.4
1990	2.49
1991	2.57
1992	2.66
1993	2.76
1994	2.85
1995	2.95
1996	3.04
1997	3.14
1998	3.24
1999	3.34
2000	3.44
2001	3.54
2002	3.65
2003	3.76
2004	3.87
2005	3.98
2006	4.09
2007	4.2
2008	4.32
2009	4.44
2010	4.56
2011	4.68
2012	4.8
2013	4.93
2014	5.05
2015	5.18