| March 1 - 31, 2012 | $100.24 | Jan-12 | | February 1 - 29, 2012 | $98.51 | Dec-11 | | January 1 - 31, 2012 | $97.17 | Nov-11 | | December 1 - 31, 2011 | $86.41 | Oct-11 | | November 1 - 30, 2011 | $85.61 | Sept-11 | | October 1 - 31, 2011 | $86.33 | Aug-11 | | September 1 - 30, 2011 | $97.26 | Jul-11 | | August 1 - 31, 2011 | $96.29 | Jun-11 | | July 1 - 31, 2011 | $101.33 | May-11 | | June 1 - 30, 2011 | $110.04 | Apr-11 | | May 1 - 31, 2011 | $102.94 | Mar-11 | | April 1 - 30, 2011 | $89.58 | Feb-11 | | March 1 - 31, 2011 | $89.42 | Jan-11 | | February 1 - 28, 2011 | $89.04 | Dec-10 | | January 1 - 31, 2011 | $84.14 | Nov-10 | | December 1 - 31, 2010 | $81.90 | Oct-10 | | November 1 - 30, 2010 | $75.24 | Sep-10 | | October 1 - 31, 2010 | $76.82 | Aug-10 | | September 1 - 30, 2010 | $76.18 | Jul-10 | | August 1 - 31, 2010 | $75.35 | Jun-10 | | July 1 - 31, 2010 | $74.07 | May-10 | | June 1 - 30, 2010 | $84.48 | Apr-10 | | May 1 - 31, 2010 | $81.24 | Mar-10 | | April 1 - 30, 2010 | $76.42 | Feb-10 | | March 1 - 31, 2010 | $78.22 | Jan-10 | | February 1 - 28, 2010 | $74.30 | Dec-09 | | January 1 - 31, 2010 | $78.08 | Nov-09 | | December 1 - 31, 2009 | $75.82 | Oct-09 | | November 1 - 30, 2009 | $69.46 | Sep-09 | | October 1 - 31, 2009 | $71.06 | Aug-09 | | September 1 - 30, 2009 | $64.09 | Jul-09 | | August 1 - 31, 2009 | $69.98 | Jun-09 | | July 1 - 31, 2009 | $59.16 | May-09 | | June 1 - 30, 2009 | $49.75 | Apr-09 | | May 1 - 31, 2009 | $47.98 | Mar-09 | | April 1 - 30, 2009 | $39.16 | Feb-09 | | March 1 - 31, 2009 | $41.74 | Jan-09 | | February 1 - 28, 2009 | $41.43 | Dec-08 | | January 1 - 31, 2009 | $57.44 | Nov-08 |
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