Year	Years
1970	1.95
1971	2.01
1972	2.08
1973	2.14
1974	2.21
1975	2.28
1976	2.35
1977	2.42
1978	2.49
1979	2.57
1980	2.65
1981	2.73
1982	2.81
1983	2.89
1984	2.98
1985	3.07
1986	3.16
1987	3.25
1988	3.35
1989	3.44
1990	3.54
1991	3.64
1992	3.75
1993	3.85
1994	3.96
1995	4.07
1996	4.18
1997	4.3
1998	4.41
1999	4.53
2000	4.65
2001	4.78
2002	4.9
2003	5.03
2004	5.16
2005	5.29
2006	5.42
2007	5.56
2008	5.69
2009	5.83
2010	5.97
2011	6.12
2012	6.26
2013	6.41
2014	6.56
2015	6.71