Year	Years
1970	1.26
1971	1.3
1972	1.34
1973	1.38
1974	1.42
1975	1.47
1976	1.51
1977	1.56
1978	1.61
1979	1.66
1980	1.72
1981	1.78
1982	1.83
1983	1.9
1984	1.96
1985	2.03
1986	2.1
1987	2.18
1988	2.26
1989	2.35
1990	2.44
1991	2.53
1992	2.63
1993	2.74
1994	2.85
1995	2.97
1996	3.04
1997	3.13
1998	3.21
1999	3.29
2000	3.37
2001	3.46
2002	3.54
2003	3.63
2004	3.72
2005	3.81
2006	3.9
2007	3.99
2008	4.09
2009	4.18
2010	4.28
2011	4.38
2012	4.48
2013	4.58
2014	4.68
2015	4.79