Year	Years
1970	1.55
1971	1.6
1972	1.65
1973	1.71
1974	1.76
1975	1.81
1976	1.87
1977	1.93
1978	1.99
1979	2.05
1980	2.11
1981	2.18
1982	2.24
1983	2.31
1984	2.38
1985	2.45
1986	2.52
1987	2.59
1988	2.67
1989	2.75
1990	2.82
1991	2.9
1992	2.99
1993	3.07
1994	3.15
1995	3.24
1996	3.33
1997	3.42
1998	3.51
1999	3.6
2000	3.7
2001	3.8
2002	3.9
2003	4
2004	4.11
2005	4.21
2006	4.32
2007	4.44
2008	4.55
2009	4.67
2010	4.78
2011	4.91
2012	5.03
2013	5.15
2014	5.28
2015	5.41