Until the end of 2018, WBL published a periodic bulletin (quarterly for 2018, 6 times per year before that).

2018:  January-March       April-June      July-September     October-December

2017:  January-February     March-April     May-June     July-August     September-October     November-December

2016:  January-February     March-April     May-June     July-August     September-October     November-December

2015:  January-February     March-April     May-June     July-August     September-October     November-December

2014:  January-February     March-April     May-June     July-August     September-October     November-December

2013:  January-February     March-April     May-June     July-August     September-October     November-December

2012:  January-February     March-April     May-June     July-August     September-October     November-December

2011:  January-February     March-April     May-June     July-August     September-October     November-December

2010:  January-February     March-April                          July-August     September-October     November-December

2009:  January-February     March-April     May-June     July-August     September-October     November-December

2008:  January-February     March-April     May-June     July-August     September-October     November-December

2007:  January-February     March-April     May-June     July-August     September-October     November-December

2006:  January-February     March-April     May-June     July-August     September-October     November-December

2005:  January-February     March-April     May-June     July-August     September-October     November-December

2004:  January-February     March-April     May-June     July-August     September-October     November-December

2003:  January-February     March-April     May-June     July-August     September-October     November-December

2002:  July-August     September-October     November-December