Year	Years
1970	1.95
1971	2.01
1972	2.07
1973	2.13
1974	2.2
1975	2.26
1976	2.33
1977	2.4
1978	2.47
1979	2.54
1980	2.62
1981	2.69
1982	2.77
1983	2.85
1984	2.94
1985	3.02
1986	3.11
1987	3.19
1988	3.28
1989	3.38
1990	3.47
1991	3.57
1992	3.66
1993	3.77
1994	3.87
1995	3.97
1996	4.08
1997	4.19
1998	4.3
1999	4.42
2000	4.54
2001	4.66
2002	4.78
2003	4.9
2004	5.03
2005	5.16
2006	5.29
2007	5.43
2008	5.56
2009	5.7
2010	5.84
2011	5.99
2012	6.13
2013	6.28
2014	6.43
2015	6.58