Year	Years
1970	1.84
1971	1.89
1972	1.94
1973	1.99
1974	2.04
1975	2.1
1976	2.15
1977	2.21
1978	2.26
1979	2.32
1980	2.38
1981	2.44
1982	2.51
1983	2.57
1984	2.64
1985	2.71
1986	2.77
1987	2.85
1988	2.92
1989	2.99
1990	3.07
1991	3.14
1992	3.22
1993	3.3
1994	3.39
1995	3.47
1996	3.55
1997	3.64
1998	3.72
1999	3.81
2000	3.9
2001	3.99
2002	4.08
2003	4.18
2004	4.27
2005	4.37
2006	4.47
2007	4.57
2008	4.67
2009	4.77
2010	4.88
2011	4.98
2012	5.09
2013	5.2
2014	5.31
2015	5.42