Year	2011 U.S. Dollars
1970-01-01	23.25
1971-01-01	24.38
1972-01-01	25.68
1973-01-01	26.98
1974-01-01	27.15
1975-01-01	28.29
1976-01-01	29.36
1977-01-01	30.44
1978-01-01	31.26
1979-01-01	32.34
1980-01-01	32.03
1981-01-01	32.81
1982-01-01	33.72
1983-01-01	34.70
1984-01-01	35.74
1985-01-01	36.65
1986-01-01	37.50
1987-01-01	38.27
1988-01-01	38.96
1989-01-01	39.80
1990-01-01	41.03
1991-01-01	41.95
1992-01-01	42.72
1993-01-01	43.34
1994-01-01	46.14
1995-01-01	47.06
1996-01-01	48.12
1997-01-01	48.43
1998-01-01	48.26
1999-01-01	48.73
2000-01-01	49.71
2001-01-01	49.45
2002-01-01	49.90
2003-01-01	50.76
2004-01-01	52.13
2005-01-01	52.86
2006-01-01	53.31
2007-01-01	53.23
2008-01-01	51.92
2009-01-01	50.90
2010-01-01	52.72
2011-01-01	53.20