Year	2011 U.S. Dollars
1977-01-01	25.19
1978-01-01	26.52
1979-01-01	27.90
1980-01-01	29.16
1981-01-01	30.29
1982-01-01	30.94
1983-01-01	32.17
1984-01-01	34.21
1985-01-01	35.74
1986-01-01	36.07
1987-01-01	37.41
1988-01-01	37.88
1989-01-01	38.12
1990-01-01	38.11
1991-01-01	38.82
1992-01-01	39.82
1993-01-01	40.79
1994-01-01	42.04
1995-01-01	42.19
1996-01-01	42.61
1997-01-01	42.72
1998-01-01	42.64
1999-01-01	42.69
2000-01-01	42.71
2001-01-01	42.75
2002-01-01	42.91
2003-01-01	43.23
2004-01-01	43.45
2005-01-01	43.70
2006-01-01	44.07
2007-01-01	44.66
2008-01-01	45.01
2009-01-01	46.25
2010-01-01	47.32
2011-01-01	48.13