By my knowledge, currently the trader inventory is weighted random based on type.
But I think it could be weighted based on the Ideology settings as well.
In the basegame the traders have no way to predict what the colony might want. But with Ideology, they can. They know that the Muffalo Worshippers will propably buy Muffalos. And will not buy muffalo meat.
The guys having specific clothing rules can propably use more of that clothing.