Year	Years
1970	1.9
1971	1.96
1972	2.02
1973	2.09
1974	2.15
1975	2.22
1976	2.29
1977	2.36
1978	2.43
1979	2.51
1980	2.58
1981	2.66
1982	2.74
1983	2.82
1984	2.91
1985	3
1986	3.08
1987	3.18
1988	3.27
1989	3.37
1990	3.46
1991	3.56
1992	3.67
1993	3.77
1994	3.88
1995	3.99
1996	4.11
1997	4.22
1998	4.34
1999	4.46
2000	4.58
2001	4.7
2002	4.83
2003	4.96
2004	5.09
2005	5.22
2006	5.36
2007	5.49
2008	5.63
2009	5.77
2010	5.91
2011	6.05
2012	6.2
2013	6.34
2014	6.49
2015	6.64