Thanks. I have a feeling that most of those outliers contributed by trash merited threads, so it's good if I can get dataset on merit distribution over boards.
If I can have them [merit distribution over boards per week], I can plot more meaningful box plots.
I will also collect data posted by LoyceV to make time series analysis and find out whether there have been break trend at some points of time.

This one has been in my TO DO list.