I'm not sure if this information is documented anywhere, and I'm hoping you awesome people can splain it to me.
I embarked on a map with a TALL ridge down the center of the site, and am in the process of carving most of the ridge away to make my fortress. The last fortress that I tried this with, I mostly let the rocks lie where they were mined, and made a very basic dorm/hospital/dining room/farm setup to keep the dorfs in the mood to work, and a simple crafting industry to use up the waste shells and buy booze. And after two years, I had a population of less than 20.
In the current fortress, to date, I've produced almost NOTHING but an apartment for my bookkeeper/broker and a pile of turtle-shell crafts to trade for booze. And PILES and piles and piles of rocks. There's no dining room, no hospital, not even (yet) a functioning well. And yet, I get a 8-10 migrants every season. It's autumn of year 2, the river just froze over, I'm up to 45-something dorfs who have decimated my booze and food supplies, and this fortress WILL starve and/or thirst to death before spring. The only difference I can think of is, when I was excavating the cistern for the proposed well, I had to run a lengthy aqueduct, and I ended up marking all the rock from the plumbing to be dumped (I hate for it to end up in the water, inaccessible). The garbage zone is inside the fortress, and my question is this: By moving the rock, did I somehow claim it as a 'product' of my fortress? If I set my garbage zone on an outside tile, would it NOT claim the garbage on my tax return? Why am I awash in glassblowers and potash makers when my entire fortress literally consists of 6 11x 11 rooms??