How does TRADE work in the game?

[socal_infidel]

@Alpaca

Yeah, I'd been trying to figure out how to increase the distances for awhile. Part of an effort to increase the emphasis on trade income and decrease the amount of income you get from farms. It just struck me as unrealistic (or maybe just unsatisfying) at how short the sea trade routes were in this game.

Especially if you check out some of these maps:

[Foz]

@Alpaca: Yeah I know that's why... I just wanted to point out that the wharf buildings at least aren't entirely useless

@SI: Nice find. I agree about trade routes seeming too short... and was wondering myself where this was controlled. How much does the value of the average trade route seem to go up when you allow them to be 4 times longer (400)? I would suspect quite a bit, because it seems like the length of the route affects its value. Not only that, but you now give each port far wider choices of where to export to, which means they can also select more compatible cities to trade with, more easily avoiding resource overlap and the lost revenue it brings.

On a side note, when I see info like this, I always end up trying to think up more useful applications than just getting something we've been wanting (always nice). What came to mind for this is that it might help the AI considerably to have all the extra income that longer trade routes are bound to be generating. AI right now is excessively good at using up every last florin at its disposal, it just seems to run short of cash too quickly to get everything done that it needs to - it eats with its eyes, not its stomach. So, the influx of money might actually help the AI function efficiently by allowing it to actually do all the stuff it wants to. Granted the player may then be rolling in obscene amounts of money, but it's probably best to err on that side of things so the AI can at least put up a good fight. Besides, the player will probably have more trouble figuring out good uses for all that cash.

If you've played much with the higher distance, SI, could you comment a bit on what it seems to have done to the AI factions, if anything? I'm interested now

[alpaca]

The royal pain in the butt with the AI is that it will always build buildings in every city (because of the automation), and then won't have much money left for units, which it will invest in cheap ones that are of course relatively costly to maintain and which it can't disband.
So the AI will often go broke if you don't play on VH where it has a cheat of 10k per round (and even then it'll sometimes happen)

[socal_infidel]

Just did some testing and it appears that the increased trade distances not only doesn't help sea trade income, but in fact, hurts it.

This was done using my custom mod (which substantially increases trade income and reduces farm and tax income).

Genoa - port_to_port_mp value set at default 100:

Trades with Toulouse



Toluouse - port_to_port_mp value set at default 100:

Trades with Genoa



Genoa - port_to_port_mp value set at 400:

Trades with Bologna:



Toulouse - port_to_port_mp value set at 400:

Trades with Rome



It looks like that with the increased distance modifier, trade routes are chosen based on the furthest port you can reach. Not on whether you can actually make more trading with that port. It's not like Genoa ditched Toulouse (or vice versa) for a more lucrative trading partner in this case, so it must just go for the furthest port within distance (just a guess).

[alpaca]

Aaah great, suddenly the name makes sense!
It's probably a setting how far the port the settlement trades with must be away from it at the very least. So if you set this to 400, you'll get trade routes only with settlements that are at least 400 mp away.

Incidentally, it looks like distance is detrimental to trade income which is a bit strange (notice how it exports the same wares to Genoa and Rome, but Rome only generates a third of the revenue - or did you sign a trade agreement with Milan but not with the Papacy?).

[socal_infidel]

@alpaca

Come to think of it, in this particular set-up of my ongoing WIP mod, I had Milan and HRE began the game as allies with trade rights (to simulate vassal-ship). France and Milan had no such treaties.

So maybe once Milan could reach Bologna the game had Genoa open up trade with Bologna (its ally and whom it held trade rights with) instead of Toulouse. In which case, Toulouse sought out the next-best port to trade with - Rome in this instance.

I'll have to do more testing when I get home from work. But it does seem strange that Toulouse received substantially less income from the exact same exports when it was trading with Rome as opposed to Genoa, even though Rome is further away. So who knows how trade is calculated...

[Belisarius Invictus]

This is great stuff. What you might want to do is create a test where you control all or almost all of the provinces in the game, so that there's a level playing field and so you can see all of the financial data.

One problem I see is how to make a province like Venice have its historical trade importance. Obviously Venice didn't do that much trade because it manufactured more products... it simply was very good at trading goods from other nations. So, I would think that means trade would be more a function of the size of your port... but then everyone could build huge ports in every single coastal province, which doesn't make sense. Basically, there needs to be a reason why some cities gain importance over others.

[Foz]

Aaah great, suddenly the name makes sense!
It's probably a setting how far the port the settlement trades with must be away from it at the very least. So if you set this to 400, you'll get trade routes only with settlements that are at least 400 mp away.

I concur. I would guess that its primary purpose is to prevent neighboring ports from trading with each other.

I'll see if I can do some tests on a saved game where I own the British Isles, Europe, and some extra, and see what happens to my trade (if it applies to a saved game, which I think it will).

[Foz]

Here are the results:

This first one is the base summary screen for the game with default trade min distance (100).



Next is what happens when I set the distance to 400.



And finally here is what happens with it set to 0.



As you can see, the shorter trade min distance does provide better trade income, so it seems for certain that shorter routes are inherently more valuable (though obviously a longer route could still be more profitable if there is less resource overlap and therefore it trades more resources). This may reflect a correct economic view most of the time - a longer route would have less trips total since it takes so much longer to reach the destination, or else would require more vessels (bigger investment and operating costs) to have the same frequency of arrival. Either way you look at it, it would be more profitable to trade 3 times as often with your neighbor than it would be to trade with a city 3 times further away, even if that city would offer you a bit more for the cargo.

As a side note to this, there may in fact be no max trading distance - it's in the city's interest to trade as close to home as possible, so there should be no need for an upper limit ever.