Year	2011 U.S. Dollars
1970-01-01	30.90
1971-01-01	32.08
1972-01-01	32.88
1973-01-01	33.70
1974-01-01	33.40
1975-01-01	34.31
1976-01-01	35.13
1977-01-01	35.50
1978-01-01	35.79
1979-01-01	35.94
1980-01-01	35.94
1981-01-01	36.78
1982-01-01	36.61
1983-01-01	37.59
1984-01-01	38.35
1985-01-01	39.05
1986-01-01	39.93
1987-01-01	40.12
1988-01-01	40.56
1989-01-01	40.88
1990-01-01	41.57
1991-01-01	42.07
1992-01-01	43.47
1993-01-01	43.68
1994-01-01	44.08
1995-01-01	44.10
1996-01-01	45.19
1997-01-01	45.86
1998-01-01	46.85
1999-01-01	48.17
2000-01-01	49.50
2001-01-01	50.66
2002-01-01	52.25
2003-01-01	53.86
2004-01-01	55.11
2005-01-01	55.94
2006-01-01	56.40
2007-01-01	57.08
2008-01-01	57.51
2009-01-01	59.00
2010-01-01	60.41
2011-01-01	60.59