Year	Years
1970	1.86
1971	1.92
1972	1.98
1973	2.04
1974	2.1
1975	2.16
1976	2.23
1977	2.3
1978	2.37
1979	2.44
1980	2.51
1981	2.59
1982	2.66
1983	2.74
1984	2.82
1985	2.91
1986	2.99
1987	3.08
1988	3.17
1989	3.26
1990	3.35
1991	3.45
1992	3.55
1993	3.65
1994	3.75
1995	3.85
1996	3.96
1997	4.07
1998	4.18
1999	4.3
2000	4.41
2001	4.53
2002	4.65
2003	4.78
2004	4.9
2005	5.03
2006	5.16
2007	5.29
2008	5.42
2009	5.56
2010	5.7
2011	5.84
2012	5.98
2013	6.12
2014	6.27
2015	6.42