Year	2011 U.S. Dollars
1970-01-01	27.57
1971-01-01	28.98
1972-01-01	30.17
1973-01-01	32.02
1974-01-01	33.89
1975-01-01	34.94
1976-01-01	36.50
1977-01-01	37.54
1978-01-01	38.78
1979-01-01	39.27
1980-01-01	39.31
1981-01-01	39.20
1982-01-01	39.66
1983-01-01	41.24
1984-01-01	42.38
1985-01-01	43.13
1986-01-01	43.74
1987-01-01	44.27
1988-01-01	45.08
1989-01-01	45.99
1990-01-01	46.68
1991-01-01	47.21
1992-01-01	47.14
1993-01-01	47.88
1994-01-01	48.70
1995-01-01	48.75
1996-01-01	49.16
1997-01-01	50.04
1998-01-01	51.07
1999-01-01	52.23
2000-01-01	53.17
2001-01-01	53.52
2002-01-01	53.87
2003-01-01	54.61
2004-01-01	56.39
2005-01-01	57.51
2006-01-01	58.53
2007-01-01	59.44
2008-01-01	59.49
2009-01-01	58.06
2010-01-01	59.35
2011-01-01	59.49