About the generation of similar words

[Jorge_Stolfi]

Only approximately between 5% and 10% of the bursts have a core that is more frequent than its members.That is, on average the variants are much more frequent than the initial word of the burst.

Maybe the core tends to be less common because it is weirder than the peripheral members?  Like, for English, the core of the words 'this', 'that', 'these', 'thus', 'those' may be 'ths' -- if this word occurs even once, e. g. because of a typo?

Is the core generally shorter than the peripheral members?

It is good that you are now analyzing words instead of just digraphs.  But now beware that the occurrence patterns can be radically different for different words, because they have different meanings and functions.  

So don't focus only on patterns and statistics that are common to all words.  Pay attention to individual words (or word clusters) that deviate from the general patterns... 

All the best, --stolfi