Year	Years
1970	1.83
1971	1.87
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	2.39
1981	2.45
1982	2.52
1983	2.59
1984	2.66
1985	2.73
1986	2.8
1987	2.88
1988	2.96
1989	3.04
1990	3.12
1991	3.21
1992	3.29
1993	3.38
1994	3.47
1995	3.57
1996	3.67
1997	3.77
1998	3.87
1999	3.97
2000	4.08
2001	4.18
2002	4.29
2003	4.4
2004	4.5
2005	4.61
2006	4.72
2007	4.83
2008	4.95
2009	5.06
2010	5.17
2011	5.28
2012	5.4
2013	5.51
2014	5.63
2015	5.74