ah thx for the info I kinda suspected wealth would factor in but the 1.5 multiplier for gobbos is news to me (immediately the last cage traps are dissembled ).
Another question that came to mind has it any effect if you kill the notables of a civilisation (General/King etc.) ?
The reason it is news to you is because it doesn't exist. The only reason that fort's get larger sieges later on is just a combination of wealth increase and a slow increase over time. Whether or not you actually kill the invaders has no effect upon the numbers.
As for killing the notables, once a king/general is slain their civilization will no longer have access to any creatures tamed in world gen by that notable, which in most cases means no more sieges riding on unicorns/jabberers/giant eagles.
i was not being litteral. there is no multiplier. im just saying that
THERE ARE ALWAYS MORE!
no matter how many you kill there will always be more... always
My theory on goblins is that they reproduce like rabbits and, being immune to hunger or thirst or old age, do so without natural limits.
It gets very crowded in the goblin fortresses. They have an unlimited supply of metals from their thriving bold recycling industry, so they outfit surplus members of the population with basic weapons and send them on sieges that hardly ever come back solely to keep the crowding down. They'd just toss their idiots and surplus goblins into lava themselves if they had the heart.
Elves have a similar overpopulation problem because they're immortal, but have solved the problem of living forever with dendrophilia, homosexuality and cannibalism.