a review of the most underappreciated building of CIV: the harbor

[DeepO]

Originally posted by Blake
The "Good trade route attraction" effect indeed exists, and is at the expense of other cities. In other words, the harbor cities get better trade routes and other cities get poorer trade routes. There is very much net benefit to this though, it's like the harbor city gets +7 trade income and the rest of your empire loses a total of 4. The net gain would be +3, but amplified by buildings and it's more.

Indeed, this is what I wanted to say. To me, it feels similar.

So assuming there are a certain number of "Good" trade routes available, these trade routes go to the Harbor cities first. But once the good trade routes are used up, there's no real benefit from having more harbors. If your empire is large there are very real diminshing returns on the trade income from additional harbors. Most of the benefit may very well come from only 2-3 harbors, in your largest cities.

Yeah... the reason why the rule of thumb 'build harbors everywhere, asap' is working is because you will have inland cities who can't get the harbor bonus. So, in those cities where you can build harbors, they are more important than simply the 50% they are generating.

I'm not so sure on whether this division of trade routes is done at an empire level, but globally: it looks to me like building harbors early is not harming your own other cities that much, however it is harming all civs you are into contact with a little (and gaining you much)

Have the mechanisms of trade routes been determined? To me it appears that they are dependent primarly on city population and not particullary on commerce or anything else. In one game my Capital was terraformed all farms/mines, yet had the highest commerce of any city due to over 70 trade income. My capital was huge, about 26.

They are not determined, but yes, it seems like population is the only city-factor, or better put: the commerce coming from trade routes (which is pop and harbor dependent) is not related to how many commerce improvements or buildings (apart from the harbor) the city has. Building a lib doesn't increase your trade revenue, building a cottage neither.

I'm probably going to have to test this. What I suspect from intutition is that harbors simply increase the population of the city by 50% for purposes of trade income and trade route ranking, that seems like the easiest way to cause both the trade route value increase and the "trade attraction" (from a programming perspective).

I wouldn't be surprised if this is not the code behind it, but in large the game mechanic can be reduced to this rule of thumb.

DeepO

[Blake]

Yeah... the reason why the rule of thumb 'build harbors everywhere, asap' is working is because you will have inland cities who can't get the harbor bonus. So, in those cities where you can build harbors, they are more important than simply the 50% they are generating.

Ahhhh, this assumes the existence OF inland cities. Someone wanting to leverage harbors might play on a map where ALL cities can be coastal, and will then be disapointed by the average performance of harbors.
On the other hand with a Pangea or Continents map it is as you say - building harbors first in the coastal cities is indeed a most worthy investment.

[DeepO]

Originally posted by Blake

Ahhhh, this assumes the existence OF inland cities. Someone wanting to leverage harbors might play on a map where ALL cities can be coastal, and will then be disapointed by the average performance of harbors.
On the other hand with a Pangea or Continents map it is as you say - building harbors first in the coastal cities is indeed a most worthy investment.

This is also part of the reason:

I'm not so sure on whether this division of trade routes is done at an empire level, but globally: it looks to me like building harbors early is not harming your own other cities that much, however it is harming all civs you are into contact with a little (and gaining you much)

If you build harbors, you're not only 'stealing trade' from your inland or harborless cities, you're also stealing trade from other civs. I think.

DeepO

[DeepO]

Oh, and of course do you want to build harbors in large cities before smaller ones, that hasn't been mentioned but it's the same like saying you want forges in high production cities first too.

DeepO

[Blake]

If you build harbors, you're not only 'stealing trade' from your inland or harborless cities, you're also stealing trade from other civs. I think.

Oh, now I just HAVE to run some tests, because if that's true... wow. (but first, I must sleep).

[DeepO]

Originally posted by Blake

Oh, now I just HAVE to run some tests, because if that's true... wow. (but first, I must sleep).

I can't be sure as I don't know the exact algorithm, but that is surely how it feels to me. And yes, this does mean that you need to get your harbors up asap: early harbors have a much larger effect than later harbors. The moment the AIs build harbors too, the effect diminishes, of course. OTOH, if they build harbors and you don't, they are stealing away your good trade routes!

DeepO

[Blake]

Interesting. It appears the size of your city actually has nearly no effect on trade route income, it's entirely about the size of the trading city. In my test for example:

Rome: size 20.
Athens: size 5.

Rome has a trade income of 3, Athens has a trade income of 9.

The size of your city does have SOME effect, but it's extremely small.

The "+50%" is extremely ungenerous when your city is much more massive.

Effect of harbor:
Rome: +5 -> +6
Athens: +6 -> +9

In other words, if your city is already so awesome as to be attracting the good trade over harbor cities, it wont benefit much from a harbor. But harbors are extremely useful if your cities are relatively small. (as it would be on high difficulty levels)

The harbor effect is extremely strong, size 14 city with harbor has more attraction than a size 24 city without harbor.

The magnetic effect and stealing trade from other civs MAY exist. I believe each city supplies a number of trade routes, but each civ can only have at most one trade route.
Ie: In a game with 10 civs, only 4 of them would get the uber-trade from my size 26 capital, even if one civ had the 2 best trading cities, only 1 of those cities would get Rome trade)

It appears on the most part it's about stealing the trade which is there, rather than creating any new trade. I can see why an early harbor or two can be very powerful.

It makes no difference if the "tradee" is coastal or landlocked, has a harbor or not. In other words, even if nearly all cities are landlocked, you'll still gain benefit from a harbor city!

Also Merchantalism does NOT reduce the trade FROM you in way at all. In other words, it only hurts you and can't be used to deny your opponents lucrative trade income.

I'm not sure if anything here changes my play or not... but eh, it's interesting anyway. And I think it does prove there is merit to getting very early harbors.

[DeepO]

Originally posted by Blake
And I think it does prove there is merit to getting very early harbors.

I knew it!

Excellent analysis, BTW

DeepO

[Heroes]

Originally posted by Blake
Here's my observations on Harbors after playing with them and observing.

The "Good trade route attraction" effect indeed exists, and is at the expense of other cities. In other words, the harbor cities get better trade routes and other cities get poorer trade routes. There is very much net benefit to this though, it's like the harbor city gets +7 trade income and the rest of your empire loses a total of 4. The net gain would be +3, but amplified by buildings and it's more.

So assuming there are a certain number of "Good" trade routes available, these trade routes go to the Harbor cities first. But once the good trade routes are used up, there's no real benefit from having more harbors. If your empire is large there are very real diminshing returns on the trade income from additional harbors. Most of the benefit may very well come from only 2-3 harbors, in your largest cities.

If my observations and assessments are correct, then there is a very real benefit to building a harbor asap in your largest city, the harbor will attract the best trade routes and be an ideal candidate for an Acadamy.

The value of harbors in smaller cities is very, very questionable.

Have the mechanisms of trade routes been determined? To me it appears that they are dependent primarly on city population and not particullary on commerce or anything else. In one game my Capital was terraformed all farms/mines, yet had the highest commerce of any city due to over 70 trade income. My capital was huge, about 26.

I'm probably going to have to test this. What I suspect from intutition is that harbors simply increase the population of the city by 50% for purposes of trade income and trade route ranking, that seems like the easiest way to cause both the trade route value increase and the "trade attraction" (from a programming perspective).

Interesting observation, thanks!
Do you have any idea about foreign vs. domestic trade routes? It looks like that trade route to a foreign city always earns more than a domestic one. However, representation + mercantillism is a powerful combination, for +3 beaker to each free specialist, but it forbids foreign trade route. So the big question is, mercantillism or free market?

[Blake]

domestic trade routes are worth waaaaay waaaay less. Like maybe 3-4g if you're lucky, while foreign can easily be 10-14g.

It's worth noting you need open borders to get foreign trade routes, the more open borders, the more good trade routes. If everyone hates you, you may as well run merc...

Basically, look at your biggest cities, and know that the trade income will be about 1/4 or worse under merc. Weigh that up vs the specialist boost in smaller cities.

Also, relatively speaking, the larger your empire the better merc is. If you have 4x as many cities as your allies then most of them wont be getting good trade routes.

I personally think the most compelling reason to use Merc is to get a free artist (and thus free culture) in new colonies.

[DeepO]

I didn't want this post to go to waste, and perhaps I can poke Blake around to do some more of these excellent tests

Keep in mind I am not running with background information here: this all comes from observations, not from knowledge.

Originally posted by Blake
Interesting. It appears the size of your city actually has nearly no effect on trade route income, it's entirely about the size of the trading city. In my test for example:

Rome: size 20.
Athens: size 5.

Rome has a trade income of 3, Athens has a trade income of 9.

So, the mechanic goes something like: all cities offer a number of trade routes. These are put on a list. When picking combinations, your best trade cities will get the best trade cities (maining those cities that are large, or/and have habors).

The choice of which city will be your trade partner (or tradee) is only partly dependent on size. However, what you gain from a trade route does not take into account the harbor of the tradee, just its size.

Is this correct? Do harbors in AI cities also put them higher on the list, so to speak? So, if an AI builds a harbor in a size 9 city, while it has a harborless size 12 city, the size 9 one will get picked for your best trading city as tradee?

And, it's logical that trade income depends on the quality of the tradee (and not on your own size), but is this only size dependent, and not harbor dependent? You could for instance have two medium size cities trading together, both with harbors, and both with high trade income...

Last question: does distance matter?

The size of your city does have SOME effect, but it's extremely small.

Might be due to roundings, or a secundary effect from something else. Roundings are not always straigthforward in CIV, they happen frequently, and create little jumps that are seemingly chaotic in nature.

The harbor effect is extremely strong, size 14 city with harbor has more attraction than a size 24 city without harbor.

Is it by any chance doubling its attraction? Meaning that e.g. size 24 cities will still beat size 13 harbor cities, but not size 12 harbor cities?

The magnetic effect and stealing trade from other civs MAY exist. I believe each city supplies a number of trade routes, but each civ can only have at most one trade route.
Ie: In a game with 10 civs, only 4 of them would get the uber-trade from my size 26 capital, even if one civ had the 2 best trading cities, only 1 of those cities would get Rome trade)

4 trade routes... by any chance tha amount of trade routes you could have in a city at that moment? Makes sense: if you can have 4 trade routes coming in, you're also sending out 4 trade routes going out.

Also, one city per empire makes sense as well. It could be that this limitation is lifted when only 2 civs are in contact (or have OB) together. You're only reporting on large games, with more civs than trade routes available.

It appears on the most part it's about stealing the trade which is there, rather than creating any new trade. I can see why an early harbor or two can be very powerful.

So, the magnet effect only has to do with stealing, while the 50% increase has to do with creating extra trade.

Both of them play at all times in the game though.
- Early on, you want to steal trade from the rest of the world. By building harbors when others don't have them, you are putting your own sizes at virtual higher pop in 'the list'. Which means you are getting more trade.
- Later, it more becomes a thing of denial: you don't want to have others stealing your trade routes by building harbors in cities which are smaller than your own! You won't gain trade, but at least you're not losing them
- In both cases, the 50% extra gives a flat bonus. Early harbors would probably be worth it even without the 50% bonus...

It makes no difference if the "tradee" is coastal or landlocked, has a harbor or not. In other words, even if nearly all cities are landlocked, you'll still gain benefit from a harbor city!

Ah... forget the harbor of the tradee then Distance is no factor either? I surely would have thought it would be...

Also Merchantalism does NOT reduce the trade FROM you in way at all. In other words, it only hurts you and can't be used to deny your opponents lucrative trade income.

This is something I expected a long time before: when running Merc, you can see in F9 that you're still exporting stuff, only have 0 import.

That ratio (import/export) becomes a good indicator of how trade-happy your empire is.
- More import: more harbors, a larger empire, or larger cities. Also more OB than average
- More export: Merc, too few harbors, a small empire with small cities. Or not enough OB's compared to others.

I'm not sure if anything here changes my play or not... but eh, it's interesting anyway. And I think it does prove there is merit to getting very early harbors.

It won't change my play, I love harbors already But this does make clear where you want to harbors specifically. Building a harbor in small, or fishermen's villages makes even more sense: it will take ages to complete a forge or granary, all this time you want to pretend your a big, healthy, tradeable city and thus get the better trade deals.

DeepO

[Blake]

I'll just reiterate:

Your city size: While city size and harbor presence has a large "attraction" effect, it only has a small effect on the actual value of the incoming trade routes.
Lets talk about Rome trading with Athens and assume there are no other cities trying to steal the trade from them.

Athens is size 10.

Say Rome is also size 10. Incoming trade might be 6. Then Rome grows to size 20. Incoming trade might only be 7 now. But most the benefit of Rome growing larger has gone to Athens.

The harbor, allows a small city to "catch up" size-wise with a larger trader partner, it seems the game penalizes lopsided trades. The harbor seems to allow a small city to get closer to the full value of the trade from a larger city, but doesn't significantly increase the income of a large city trading with a smaller city. It's certainly not a flat +50%, it's a lot more complex than that. It might just be capped at +50%.

In short, a harbor does allow a small city to act like a larger city for incoming trade purposes, it doesn't really allow a huge city to act like an even huger city.

Something I assume, but haven’t tested (yet) is that the # of incoming trade routes = the number of outgoing trade routes. Rome has 4 incoming trade routes, (up to) 4 other cities in the world have trade routes from Rome.
So if you get the Great Lighthouse, you may also help civs you are trading with!

But I think this would only be significant if you have a large number of trading partners.

I also believe the Great Lighthouses steals trade from your other cities and gives it to your best coastal cities. In other words, it's another "concentration of good trade" effect. But of course your other cities get (smaller) trade routes to replace the ones they lost so the effect is still very much a net positive. Also if your civ is very small then a lot of good incoming trade routes would have "nowhere to go", these routes would be enabled by the Great Lighthouse and it would thus have a proportionally larger effect on your income than it would for a larger civ. (but a larger civ will always gain more net benefit)

In fact the trade model in general seems to be one thing that enables a smaller civ to prosper amongst the giants. It certainly is a very interesting system.

[Heroes]

Originally posted by Blake
In fact the trade model in general seems to be one thing that enables a smaller civ to prosper amongst the giants. It certainly is a very interesting system.

I notice that there is a natural tendency for backwards civ to catch up in civ 3. For example, if you are an age behind, selling a lux to a big civ could net you a tech. The more civs know a tech, the cheaper for you to research it. Therefore in the long run every civ would become more or less equally advanced (if no war!). In civ 4 this trend is also present, for example in this trade route thing. However, tech trade and broking is much harder. Whether it's harder or easier to catch up in civ 4 comparing to 3, this is still an open question to me.

[Blake]

Okay the latest game I actually applied some lessons from the Harbor research. My capital I founded on the coast, and also got a quick acadamy. As such it had a better tech multiplier. However my 3rd city actually managed to grow faster than my capital and was also a harbor city. I tweaked food until the capital was growing faster, thus I kept the best trade routes on the Capital. The benefit of this was minor but not entirely insignificant, basically the best 4 trade routes were:
6/6/5/5, with the next best 4 being 4/4/4/4. Thus by the population balancing I boosted commerce at the capital by 6, which put through the acadamy only came to +3, but oh well, better than nothing.

It seems that if your capital and another city are both the same size, the good trade goes to your capital. Probably a city order thing, it's handy anyway since you probably want it going to the Capital.

[Cort Haus]

Harbors on isolated continents probably need to wait until oceanic trade is enabled with Astronomy (unless health is needed). When it came round in my current game the magnet effect boosted some cities from 2/2 to 6/6. Seeing that boost is worth even more as the AI is denied those routes was very satisfying.