Year	Years
1970	1.48
1971	1.52
1972	1.56
1973	1.61
1974	1.65
1975	1.69
1976	1.74
1977	1.78
1978	1.83
1979	1.88
1980	1.93
1981	1.98
1982	2.03
1983	2.08
1984	2.14
1985	2.19
1986	2.25
1987	2.31
1988	2.37
1989	2.43
1990	2.49
1991	2.55
1992	2.62
1993	2.68
1994	2.75
1995	2.82
1996	2.9
1997	2.97
1998	3.05
1999	3.12
2000	3.2
2001	3.28
2002	3.36
2003	3.44
2004	3.53
2005	3.61
2006	3.7
2007	3.79
2008	3.88
2009	3.97
2010	4.06
2011	4.15
2012	4.25
2013	4.34
2014	4.44
2015	4.54