Year	Years
1970	1.89
1971	1.94
1972	1.99
1973	2.04
1974	2.09
1975	2.15
1976	2.21
1977	2.26
1978	2.32
1979	2.38
1980	2.45
1981	2.51
1982	2.58
1983	2.64
1984	2.71
1985	2.78
1986	2.85
1987	2.93
1988	3
1989	3.08
1990	3.16
1991	3.24
1992	3.32
1993	3.41
1994	3.5
1995	3.59
1996	3.68
1997	3.77
1998	3.87
1999	3.97
2000	4.06
2001	4.16
2002	4.26
2003	4.36
2004	4.47
2005	4.57
2006	4.67
2007	4.78
2008	4.89
2009	4.99
2010	5.1
2011	5.21
2012	5.32
2013	5.44
2014	5.55
2015	5.66