Year	Years
1970	1.72
1971	1.77
1972	1.83
1973	1.88
1974	1.94
1975	2
1976	2.07
1977	2.13
1978	2.2
1979	2.26
1980	2.33
1981	2.4
1982	2.48
1983	2.55
1984	2.63
1985	2.71
1986	2.79
1987	2.88
1988	2.96
1989	3.05
1990	3.14
1991	3.23
1992	3.32
1993	3.42
1994	3.52
1995	3.62
1996	3.72
1997	3.83
1998	3.94
1999	4.05
2000	4.16
2001	4.27
2002	4.39
2003	4.51
2004	4.63
2005	4.75
2006	4.87
2007	5
2008	5.13
2009	5.26
2010	5.39
2011	5.52
2012	5.66
2013	5.8
2014	5.94
2015	6.08