Year	2011 U.S. Dollars
1980-01-01	31.46
1981-01-01	31.65
1982-01-01	31.52
1983-01-01	31.80
1984-01-01	33.01
1985-01-01	33.68
1986-01-01	34.25
1987-01-01	34.90
1988-01-01	35.91
1989-01-01	37.19
1990-01-01	37.57
1991-01-01	37.59
1992-01-01	38.09
1993-01-01	38.94
1994-01-01	40.63
1995-01-01	41.84
1996-01-01	41.78
1997-01-01	42.55
1998-01-01	42.28
1999-01-01	42.40
2000-01-01	43.57
2001-01-01	43.95
2002-01-01	43.70
2003-01-01	43.09
2004-01-01	43.68
2005-01-01	44.05
2006-01-01	44.26
2007-01-01	44.46
2008-01-01	44.17
2009-01-01	43.15
2010-01-01	44.28
2011-01-01	44.43