Year	Years
1970	1.99
1971	2.04
1972	2.09
1973	2.14
1974	2.2
1975	2.25
1976	2.31
1977	2.37
1978	2.43
1979	2.49
1980	2.55
1981	2.61
1982	2.68
1983	2.74
1984	2.81
1985	2.88
1986	2.95
1987	3.02
1988	3.09
1989	3.17
1990	3.24
1991	3.32
1992	3.4
1993	3.48
1994	3.56
1995	3.64
1996	3.73
1997	3.82
1998	3.9
1999	3.99
2000	4.09
2001	4.18
2002	4.27
2003	4.37
2004	4.47
2005	4.57
2006	4.67
2007	4.77
2008	4.87
2009	4.98
2010	5.08
2011	5.19
2012	5.3
2013	5.41
2014	5.52
2015	5.63