Assuming we have 7 amenities for each city, +4 campus with all of its buildings, powered, 2 Science CSs with each having 6 envoys (average scenario if we start with standard 12 CSs), double adj card & Rationalism, how much Science will we generate for different population cities?
4 Pop: Amenity 5 (Escatic) (4*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.2=51.6 Science
6 Pop: Amenity 4 (Happy) (6*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.1=48.4 Science
8 Pop: Amenity 3 (Happy) (8*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.1=49.5 Science
10 Pop: Amenity 2 (Content) (10*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.0=46 Science
12 Pop: Amenity 1 (Content) (12*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.0=47 Science
14 Pop: Amenity 0 (Content) (14*0.5+4*2+(1+2+3)*2+(2+4+8)*1.5)*1.0=48 Science
16 Pop: Amenity -1 (Displeased) (16*0.5+4*2+(1+2+3)*2+(2+4+8)*2.0)*0.9=50.4 Science
18 Pop: Amenity -2 (Displeased) (18*0.5+4*2+(1+2+3)*2+(2+4+8)*2.0)*0.9=51.3 Science
20 Pop: Amenity -3 (Unhappy) (20*0.5+4*2+(1+2+3)*2+(2+4+8)*2.0)*0.8=46.4 Science
So 4 pop yields the most science in the upcoming update, if you have 7 amenities per city.
Your example is a bit farfetched, but I think it illustrates well the 'flatness' of value between cities.
In a world where all cities have pretty much the same value, the only thing that matters is the number of cities that you own.
However, to be more precise I will add a little nuance and reformulate this statement this way: The total yield (science) output is mainly a function of the number of districts (built up with buildings) that you own and since you cannot build more than one specialty district of the same type in the same city, the number of cities that you own with that specialty district is ultimately the only thing that matters to increase that total yield output (science).
This is because civ6 puts way too much emphasis on infrastructure (capital) and not enough on population (human capital).
Currently, the main advantage of increasing population is that you unlock more district slots (ie more infrastructure).
As an illustration, if Firaxis were to implement bio weapons in the game that kill off a large proportion of a city's population, but leaves the infrastructure (districts) intact, they would do little damage to the recipient because the yields provided by that city would barely change even if more that half of its population is wiped out because the yields provided by that city mainly come from districts and buildings.
In the current incarnation of civ6, a ghost town from the depression era full of infrastructure nearly provides the same yields as a bustling city with the same kind of infrastructure.
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I identify 3 main caveats with your example that one should keep in mind:
- It is easier to achieve an adjacency of +4 in a more populous city. Since you unlock more districts per city, they can be used to increase the adjacency of the campus by placing them next to it. With pop 4 cities, even if you pair them and build all 4 districts next to each other, you can only increase the adjacency of the campi by +1 which means you absolutely need to get a +3 adjacency bonus from terrain to reach +4. If you have more populous cities, with more district slots, you can potentially place 4 districts next to a campus and increase its adjacency by +2 which means you only need to get +2 adjacency from terrain to reach +4.
- You can increase your amenities by building the necessary infrastructure (Entertainment Complexes). It is less costly to 'waste' a district slot to an EC in a taller city. If you can only build 2 districts per city (pop 4), choosing to build an EC has a greater opportunity cost. Since in your example you want to build a campus in every city, building an EC means one less CH, IZ, HS or Harbor, etc.
- You can build and develop districts faster in more populous cities, because they have higher production. The extra science can thus be expected to come online faster.
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The main giveaway I get from this is that the meta changed:
Before you wanted all your cities to get to pop 10.
Now you maybe identify a few cities which you can get to pop 15, build a few pop 7 cities where you need districts that provide regional bonuses and leave the rest as pop 4 cities.
Growing 'needlessly' cities has now a greater opportunity cost (with the increased Happy/Ecstatic bonus).
You need to identify how many districts of each type you need to reach your victory condition and identify how many pop you need to build them all and not grow further.
Buying amenities from AIs may also be more beneficial now.
Warring also has a greater opportunity cost (loss of amenity through war weariness).
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From memory, in Civ5 BNW (which is regarded as the civ game that punished the most wide play), each new city increased unhappiness by 3. Since each new pop also increased unhappiness by 1, founding a new city (with pop 1) increased unhappiness by 4 in total. If your total empire was unhappy (total unhappiness greater than total happiness), your population growth in all your cities was pretty much halted (ie much harsher than in civ6). Early happiness also came from luxuries, but workers needed 5-8 turns to improve them (ie not instantaneously improved with builder charges). You also could increase local happiness by constructing buildings (infrastructure). Gandhi had as a unique ability double unhappiness from new cities (2*3), but halved (0.5) unhappiness from population. It was regarded as promoting tall play: only after reaching pop 7 did Gandhi's cities become happier than cities from other civilizations. (Civ6 is basically Gandhi's upside ability without downside for all civilizations!)
Now why I am talking about this? By giving a fixed amenity/happiness cost to any new city, you create an "amenity cost" that needs to be recouped before becoming a net positive. Spamming low pop cities thus becomes more costly from an amenity perspective. This would counter-balance the current benefit that low pop cities get more free amenities. By removing the free amenity that each new non-capital city gets and putting back the content minimum threshold back at 0, the game has very slightly moved into that direction.
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Now, I wonder what if district buildings provided 0 yield unless they were worked by a specialist?
After all, what good is a University without professors? What good is a Factory without workers?
Why should an empty Coal plant provide any production or electricity?
Current specialist yields would be reduced to zero and replaced by the building yields.
Current building perks such as 25% experience for units for Barracks would only be applied if the Barracks is staffed.
Great Person Points would only accrue when specialists are assigned.
In this scenario, a pop 4 city with a Research Lab would only provide a near equal amount of science as a more populous city if it is able to work all 3 science building slots. If it does, it would be useless at producing nearly anything else and would be very likely to run into a food deficit (unless it is working a 6+ food tile or has buildings that provide food beyond the +2 from the city center). The only way to fill that deficit would be to run a trade route that provides food. You would thus need to go CH/Harbor + Campus in all cities to even begin to try to make this work.
I recently played the latest 6otM games which were OCC. One thing that is apparent from playing them is that any pop above 30 is nearly completely useless even in a Pingala city. You eventually run out of slots to assign population. If more districts such as EC/WP required population to be assigned to in order to provide their perk, you would never run into such a problem. In fact, if all specialty districts required population for their buildings to work you would always have more district slots available (+terrain slots) than you would have population as long as you build them when you are able to unlock them. Example, at pop 4-6, you can unlock 2 districts (with potentially 3 slots each), you thus have 6 specialty slots available for 4-6 pop. When there are more slots than population available in a city, you create a choice for the player who decides which slot he wants to work. Currently, specialty districts that provide no additional slot not only add no slot, but they take away a workable terrain slot which hurts populous cities more. (Note: I guess it is theoretically possible to run out of specialty districts (limited by district types available) to build in a city and to have all terrain tiles occupied by wonders or districts, but this would happen at a higher population threshold than currently).
Now some of these changes are easily moddable, but others not. Furthermore, the AI barely knows how to play the game as it is, I wonder how it would be able to cope with such changes. Maybe, the extra yield preferences will be enough to make the AIs assign population as specialists.
