Year	Years
1970	1.9
1971	1.96
1972	2.02
1973	2.08
1974	2.15
1975	2.22
1976	2.28
1977	2.36
1978	2.43
1979	2.5
1980	2.58
1981	2.66
1982	2.74
1983	2.83
1984	2.91
1985	3
1986	3.09
1987	3.18
1988	3.28
1989	3.38
1990	3.48
1991	3.58
1992	3.68
1993	3.79
1994	3.9
1995	4.02
1996	4.14
1997	4.27
1998	4.4
1999	4.53
2000	4.66
2001	4.79
2002	4.93
2003	5.07
2004	5.21
2005	5.35
2006	5.49
2007	5.64
2008	5.78
2009	5.93
2010	6.08
2011	6.23
2012	6.38
2013	6.54
2014	6.69
2015	6.85