Year	Years
1970	1.28
1971	1.32
1972	1.36
1973	1.41
1974	1.45
1975	1.5
1976	1.55
1977	1.6
1978	1.65
1979	1.7
1980	1.75
1981	1.81
1982	1.87
1983	1.93
1984	1.99
1985	2.05
1986	2.11
1987	2.18
1988	2.25
1989	2.32
1990	2.39
1991	2.46
1992	2.54
1993	2.61
1994	2.69
1995	2.77
1996	2.86
1997	2.94
1998	3.03
1999	3.12
2000	3.21
2001	3.31
2002	3.4
2003	3.5
2004	3.6
2005	3.7
2006	3.81
2007	3.91
2008	4.02
2009	4.13
2010	4.25
2011	4.36
2012	4.48
2013	4.6
2014	4.72
2015	4.84