What could have caused this wave of 62 immigrant dwarves

dwarf-fortress

I started playing the latest version of Dwarf Fortress yesterday. The first two migration waves carried two and four dwarves respectively. Then suddenly, when the third wave arrived, my fortress was flooded by immigrants to a total of 75 dwarves. I've never seen such a big immigration before. Was there a recent change in how immigration works? What could have caused this?

The only things I've done between the waves is fairly normal stuff: digging straight downwards without finding anything, mining out some hematite, butcher some animals, trade small amounts with the caravan, and dig a lava moat out of the volcano.

Best Answer

From the Dwarf Fortress wiki:

The first two migrant waves have a minimum size of 2 and a maximum size of 10. The size of these waves are unaffected by fortress wealth.

The third migrant wave and on are influenced by the created wealth of the fortress, with more wealth attracting more immigrants (more research is needed to determine specifics). Specifically, they're influenced by the fortress wealth as reported by the last outgoing dwarven caravan. Wealth created after the caravan leaves has no influence until the next year's caravan leaves. If the caravan fails to make it out then the fortress' wealth is not reported. The dwarven liaison does not report on fortress wealth, in those circumstances where the liaison makes it out but the caravan doesn't.

Imported wealth, caravan sales figures, absolute caravan profit and caravan profit margin either have no effect on migration numbers, or only have an effect by applying a percent modification to the numbers driven by created wealth. If a fortress manages to trade (not offer) away 100% of its created wealth then no immigrants will come the next season.

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