Year	2011 U.S. Dollars
1970-01-01	13.62
1971-01-01	14.18
1972-01-01	15.17
1973-01-01	15.78
1974-01-01	16.03
1975-01-01	16.85
1976-01-01	17.09
1977-01-01	17.29
1978-01-01	17.74
1979-01-01	18.30
1980-01-01	18.55
1981-01-01	19.26
1982-01-01	19.80
1983-01-01	20.14
1984-01-01	20.84
1985-01-01	22.22
1986-01-01	22.76
1987-01-01	23.54
1988-01-01	24.91
1989-01-01	26.19
1990-01-01	27.56
1991-01-01	28.55
1992-01-01	29.08
1993-01-01	29.85
1994-01-01	30.22
1995-01-01	30.67
1996-01-01	31.42
1997-01-01	32.19
1998-01-01	32.31
1999-01-01	33.01
2000-01-01	33.71
2001-01-01	34.43
2002-01-01	35.19
2003-01-01	35.70
2004-01-01	36.19
2005-01-01	36.62
2006-01-01	36.89
2007-01-01	37.73
2008-01-01	37.89
2009-01-01	37.37
2010-01-01	38.76
2011-01-01	39.70