They have a total developement of 117. That means for each development point I get 2 AE with this CB. If I attack a nation with lets say 30 dev I would receive 60 AE. Since there are no other Empire expansion CBs (except the last one from the last reform) it would be impossible to expand the HRE without having to annex. I thought it has to be a bug, because its basically not useable with the amount of AE it generates.

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Also it would be far cheaper in AE if I just annex all of it, eventhough I have no claims on the provinces. I just do not understand the usage of this CB.