Year	Years
1970	1.94
1971	1.99
1972	2.05
1973	2.11
1974	2.16
1975	2.23
1976	2.29
1977	2.35
1978	2.42
1979	2.49
1980	2.56
1981	2.63
1982	2.71
1983	2.79
1984	2.87
1985	2.95
1986	3.04
1987	3.13
1988	3.22
1989	3.32
1990	3.42
1991	3.53
1992	3.63
1993	3.75
1994	3.86
1995	3.98
1996	4.12
1997	4.25
1998	4.38
1999	4.52
2000	4.65
2001	4.79
2002	4.93
2003	5.07
2004	5.21
2005	5.36
2006	5.5
2007	5.64
2008	5.78
2009	5.93
2010	6.07
2011	6.21
2012	6.35
2013	6.49
2014	6.62
2015	6.76