Month    Threshold[C]
2004-Jan   37.6
2004-Feb   37.5
2004-Mar   37.4
2004-Apr   37.4
2004-May   37.3
2004-Jun   37.2
2004-Jul   37.1
2004-Aug   37.0
2004-Sep   37.0
2004-Oct   36.9
2004-Nov   36.8
2004-Dec   36.7
2005-Jan   36.6
2005-Feb   36.6
2005-Mar   36.5
2005-Apr   36.4
2005-May   36.3
2005-Jun   36.2
2005-Jul   36.2
2005-Aug   36.1
2005-Sep   36.0
2005-Oct   35.9
2005-Nov   35.8
2005-Dec   35.8
2006-Jan   35.7
2006-Feb   35.6
2006-Mar   35.5
2006-Apr   35.5
2006-May   35.4
2006-Jun   35.3
2006-Jul   35.2
2006-Aug   35.1
2006-Sep   35.1
2006-Oct   35.0
2006-Nov   34.9
2006-Dec   34.8
2007-Jan   34.7
2007-Feb   34.7
2007-Mar   34.6
2007-Apr   34.5
2007-May   34.4
2007-Jun   34.3
2007-Jul   34.3
2007-Aug   34.2
2007-Sep   34.1
2007-Oct   34.0
2007-Nov   33.9
2007-Dec   33.9
2008-Jan   33.8
2008-Feb   33.7
2008-Mar   33.6
2008-Apr   33.6
2008-May   33.5
2008-Jun   33.4
2008-Jul   33.3
2008-Aug   33.2
2008-Sep   33.2
2008-Oct   33.1
2008-Nov   33.0
2008-Dec   32.9