Year	Years
1970	1.85
1971	1.9
1972	1.96
1973	2.02
1974	2.08
1975	2.15
1976	2.22
1977	2.28
1978	2.36
1979	2.43
1980	2.51
1981	2.59
1982	2.67
1983	2.76
1984	2.84
1985	2.94
1986	3.03
1987	3.13
1988	3.23
1989	3.34
1990	3.45
1991	3.56
1992	3.68
1993	3.8
1994	3.93
1995	4.05
1996	4.18
1997	4.3
1998	4.43
1999	4.55
2000	4.68
2001	4.81
2002	4.94
2003	5.07
2004	5.19
2005	5.32
2006	5.45
2007	5.58
2008	5.71
2009	5.83
2010	5.96
2011	6.09
2012	6.21
2013	6.34
2014	6.46
2015	6.59