@LeviKornelsen A dash of it makes the world feel more real, but unless it's tied to a source of hooks I find it largely useless.
"Country X imports salt"...who cares? But "Country X has no salt, so they stole Country Y's salt mines a few years back, and now they're at war"? Now you're cooking!
If memory serves, Red Tide does a great job of making this sort of info into calls to action.
@LeviKornelsen I recall being bemused by the trade icons in the Greyhawk boxed set; kind of neat as background color, but little meaningful effect on play; it wasn't like I was going to follow the chain of imports and exports to figure out the flow of pottery across the continent.
Trade notes work as succinct leads directly to scenarios (this barony produces iron, therefore mines to explore) but otherwise only make sense if trade is a supported game activity (ala Traveller).
@LeviKornelsen I'm not really putting much thought into manufacturing.
It's raw materials where I think local economies really shape the policies of the greater setting.