Year	Years
1970	1.82
1971	1.87
1972	1.93
1973	1.99
1974	2.05
1975	2.11
1976	2.18
1977	2.24
1978	2.31
1979	2.38
1980	2.45
1981	2.53
1982	2.6
1983	2.68
1984	2.76
1985	2.84
1986	2.92
1987	3
1988	3.09
1989	3.18
1990	3.27
1991	3.36
1992	3.46
1993	3.56
1994	3.66
1995	3.76
1996	3.87
1997	3.98
1998	4.09
1999	4.2
2000	4.32
2001	4.44
2002	4.56
2003	4.69
2004	4.81
2005	4.94
2006	5.07
2007	5.2
2008	5.34
2009	5.48
2010	5.62
2011	5.76
2012	5.9
2013	6.05
2014	6.19
2015	6.34