Year	Years
1970	1.83
1971	1.88
1972	1.93
1973	1.98
1974	2.03
1975	2.09
1976	2.14
1977	2.2
1978	2.26
1979	2.32
1980	2.38
1981	2.45
1982	2.51
1983	2.58
1984	2.65
1985	2.72
1986	2.79
1987	2.87
1988	2.94
1989	3.02
1990	3.1
1991	3.18
1992	3.27
1993	3.35
1994	3.44
1995	3.53
1996	3.63
1997	3.73
1998	3.83
1999	3.93
2000	4.03
2001	4.13
2002	4.24
2003	4.34
2004	4.45
2005	4.56
2006	4.66
2007	4.77
2008	4.88
2009	4.99
2010	5.1
2011	5.22
2012	5.33
2013	5.44
2014	5.56
2015	5.67