Year	Years
1970	1.79
1971	1.84
1972	1.9
1973	1.97
1974	2.03
1975	2.09
1976	2.16
1977	2.23
1978	2.3
1979	2.37
1980	2.45
1981	2.53
1982	2.61
1983	2.69
1984	2.77
1985	2.86
1986	2.94
1987	3.04
1988	3.13
1989	3.22
1990	3.32
1991	3.42
1992	3.52
1993	3.63
1994	3.73
1995	3.84
1996	3.94
1997	4.05
1998	4.16
1999	4.27
2000	4.38
2001	4.5
2002	4.61
2003	4.73
2004	4.85
2005	4.97
2006	5.09
2007	5.21
2008	5.34
2009	5.46
2010	5.59
2011	5.72
2012	5.85
2013	5.98
2014	6.11
2015	6.24