:It's done in two steps, one that starts with the FAC logs to produce a table with a month's worth of the by-year lists like Wikipedia:Featured articles nominated in 2006 and another to parse the by-year lists to produce the WP:WBFAN table.  It looks like Wikipedia:List of Wikipedians by featured list nominations is done mostly by hand at this point.  The first step could start with the featured list logs, but unlike the second step it's not fully automated (the logs aren't quite regular enough to reliably determine who the nominator is).  What I actually do is run a script that parses the logs into an intermediate form which I check by hand against the actual logs, and then run another script using this intermediate form to generate the table format.  After updating the by-year list, the second step is done with yet another script that reads all the by-year lists and generates the WP:WBFAN table.  The second step is actually the easier one since it's fully automated, but it relies on the existence of the by-year lists.  I'd be happy to make the scripts I use to generate these lists available, but don't think I can take on generating by-year lists for featured lists.  If you (or anyone else reading these words) would like to, please let me know and I'll make the scripts available.