Year	Years
1970	1.86
1971	1.9
1972	1.95
1973	2
1974	2.06
1975	2.11
1976	2.16
1977	2.22
1978	2.28
1979	2.33
1980	2.39
1981	2.45
1982	2.52
1983	2.58
1984	2.65
1985	2.71
1986	2.78
1987	2.85
1988	2.92
1989	2.99
1990	3.07
1991	3.14
1992	3.22
1993	3.3
1994	3.38
1995	3.47
1996	3.56
1997	3.65
1998	3.74
1999	3.83
2000	3.92
2001	4.02
2002	4.11
2003	4.21
2004	4.31
2005	4.41
2006	4.51
2007	4.62
2008	4.72
2009	4.83
2010	4.93
2011	5.04
2012	5.15
2013	5.26
2014	5.38
2015	5.49