Year	Years
1970	1.26
1971	1.3
1972	1.34
1973	1.38
1974	1.43
1975	1.48
1976	1.53
1977	1.58
1978	1.63
1979	1.68
1980	1.73
1981	1.79
1982	1.85
1983	1.91
1984	1.97
1985	2.03
1986	2.1
1987	2.16
1988	2.23
1989	2.3
1990	2.37
1991	2.45
1992	2.52
1993	2.6
1994	2.68
1995	2.77
1996	2.85
1997	2.94
1998	3.02
1999	3.11
2000	3.21
2001	3.3
2002	3.4
2003	3.49
2004	3.59
2005	3.69
2006	3.8
2007	3.9
2008	4.01
2009	4.12
2010	4.23
2011	4.34
2012	4.46
2013	4.57
2014	4.69
2015	4.81