Year	Years
1970	1.82
1971	1.87
1972	1.91
1973	1.96
1974	2.01
1975	2.06
1976	2.11
1977	2.16
1978	2.22
1979	2.27
1980	2.33
1981	2.38
1982	2.44
1983	2.5
1984	2.56
1985	2.62
1986	2.68
1987	2.75
1988	2.81
1989	2.88
1990	2.95
1991	3.01
1992	3.08
1993	3.15
1994	3.23
1995	3.3
1996	3.38
1997	3.46
1998	3.55
1999	3.63
2000	3.72
2001	3.8
2002	3.89
2003	3.98
2004	4.07
2005	4.17
2006	4.26
2007	4.36
2008	4.46
2009	4.56
2010	4.66
2011	4.76
2012	4.86
2013	4.97
2014	5.07
2015	5.18