Year	Years
1970	1.99
1971	2.04
1972	2.09
1973	2.15
1974	2.2
1975	2.26
1976	2.32
1977	2.38
1978	2.44
1979	2.5
1980	2.57
1981	2.63
1982	2.7
1983	2.77
1984	2.83
1985	2.91
1986	2.98
1987	3.05
1988	3.13
1989	3.21
1990	3.29
1991	3.37
1992	3.45
1993	3.53
1994	3.62
1995	3.71
1996	3.79
1997	3.88
1998	3.97
1999	4.07
2000	4.16
2001	4.25
2002	4.35
2003	4.45
2004	4.55
2005	4.65
2006	4.75
2007	4.85
2008	4.96
2009	5.06
2010	5.17
2011	5.28
2012	5.39
2013	5.5
2014	5.62
2015	5.73