I have a factory that accepts raw materials from, lets say, a mine. If I click on that mine it shows me the financial information i.e. costs v exports. If everything from the mine ends up in the factory will the mine actually show a loss? i.e. exports zero.

The reason I am asking is to know when to build another factory. Of course you could check the input figure of the factory, but if the above is true then if the exports value from the mine is going up, then that too would indicate some resource going straight to the docks?

I'm not exactly sure how it registers on the mine itself.. BUT if you want to know when to build another factory/farm, ect.. just check your Trade tab, and click on exports.

If you either see something being exported, aka iron, you should make more industry. On the flip side, things like fish, or farm products, if they vanish from being exported, you most likely need more.

For good quality food production, you should be exporting a tiny bit of each item produced. I like to have about 1k dollars or soo of everything i make being exported, that means im about perfect as it's better to have just a little bit extra, vrs not enough.