Mod Idea - Cost of Living (& Urban Density)

Maybe high Technology should increase urban population density somewhat? I’m guessing this because of how high tech industries tend to concentrate in certain cities and attract people to move to those cities.

What would be really interesting would be policies designed specifically to increase/reduce UPD. Some ideas could include:
Urban Development Tax Breaks: through tax breaks for high-density urban development, more buildings are built in cities. This would increase UPD and the GDP somewhat, as well as private housing.

City Council Subsidies

The government subsidises the local governments of major cities in order to let them function more effectively. This increases urbanisation and approval from Socialists, and upsets Capitalists slightly.

Limit Co-living

The government places regulations on two or more unrelated people sharing a home and both contributing to its rent, this reduces Urban Population Density significantly and upsets Poor, Liberals and Youth. This sounds crazy but it has happened in a city level.

You could also use some ideas from this guy though de-urbanisation is not necessarily a good thing, he has some ideas you could use.

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An idea about core concept: What if Urban Density follows a cyclic pattern?

Core Causes:

  • GDP (+)
  • Wages (+)
  • Cost of Living (-)
  • Real Estate Bubble (-)
  • Urban Decay (-)
  • Homelessness (-)
  • Global Economy or Tourism (+)

Core Effects:

  • Real Estate Bubble (only when UD is at rise)
  • Urban Decay (a new situation, only when UD is at decline)
  • Cost of Living (+)

Expected Behaviors:

  • If Urban Density rises sharply, Real Estate Bubble is triggered, leading to lower UD in the long term (>8 turns)
  • Regardless of the causes (maybe a bubble, recession, or anything else), if UD starts to decline significantly, Urban Decay is triggered. It drags UD down even more so that the ongoing decline can persist for more turns.
  • As the original causes and Urban Decay get settled down, UD can start rising again.
  • With some stabilization efforts on UD or dedicated countermeasures for these 2 situations, you can escape this cycle.

I guess fine-tuning sensitivity of rise/decline detectors would be a challenge. Detection itself is definitely possible (I’ve tried it before) but I have to make sure these situations behave as expected. Of course the most important question would be “does it sound interesting?”

First Iteration of Urban Density & Urban Decay

  1. Icons

First of all, I’d like to mention that the Urban Decay icon in this mod is actually from Industrial Evolution mod by Gikgik. I’ve just re-created it in svg vector image format using Unemployment, Pollution Controls, and Flags on Street Corners policy icons provided by the base game (D4). The other has been, obviously, inspired by…

I created 2 candidate images for each of them and decided which one to use.

  1. Implementations (w/ screenshots)

Urban Density (in Italy mission. quite a lucky case where Real Estate Bubble didn’t end up triggering Urban Decay)

Urban Decay (in Australia mission)

Yet to playtest the mod actually. So it will take some more iterations to balance I guess. Also I’m going to re-write the description. It’s too lengthy and doesn’t really feel like describing Urban Density.

Some Undecided Things:

  • What kinds of penalties will fit with Urban Decay? It already has a link to Ghettos but still seems rather bland.
  • High Urban Density needs more distinct benefits I think. It has some but most of them seem unimportant. This actually prevents me from achieving my original intention - making high-density countries more expensive to live, which could end up just punishing high UD as there isn’t an apparent benefit.
  • Since I was unsure whether private healthcare/schools would benefit from increased urban density, I’ve left them untouched. But maybe I should just add State Healthcare cost reduction & Private Healthcare boosts for high Urban Density.
  • I added High Urban Density → Lower Mental Health link and it might not be a fair depiction.
  • This seems to be getting bigger and bigger every moment so I’m thinking about whether I should divide it into CoL Lite & CoL w/Urbanism or just push an update.

Looks fine so far. Let me know when you publish it so I can test it and give some feedback.
I do already have some points I want to share with you.
-Why does road building increase density? Roads take up a lot of space in cities so the more you build, the less dense cities get… Right?
-Wasn’t there a situation (red bubble) named urban overcrowding? You should definitely use that one in this mod.
-I think policies like Married couple tax allowance, mortgage tax relief, mansion tax, second house tax/ban, close all airports, and vertical farming subsidies should all increase urban density.
-Instead of each agricultural policy individually influencing urban density, you could just use farmer population as an influence on urban density.
-Young people often want to live in cities so maybe youth population should increase urban density.
-A very important policy to add is “zoning regulations” because this is one of the main factors in deciding where and how dense new housing projects can be. I think it should be an uncancellable policy with on the left side of the slider “Relaxed zoning regulations” which increases urban density and private housing and decrease real estate bubble and maybe homelessness. And on the right side of the slider it should say “strict zoning regulations” which should increase happiness of middle and high income (because it prevents new houses from being built in their neighborhood) and it should decrease equality, and urban density.
-Add “Highrise subsidies” as a policy that increases urban density, private housing, and happiness of high income. And decreases Real Estate Bubble.
-In the case of private Healthcare and Education. Higher urban density creates economies of scale, thus decreasing costs. Also, higher urban density means more people in the same area, so more potential customers. So, I would slightly increase private healthcare and education and maybe even make it dependent on state healthcare and education spending (with the little gear icon). And also slightly decrease the effect of private healthcare and education on income (if that is possible).

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Thanks for your input!

  • Actually, I made building less roads increase density. Below 50% = increase density. But I agree that this might be misleading. I can adjust the default value of Urban Density and make Road Building - UD link negative.
  • Urban Overcrowding was in D3: Africa but I don’t think it’s in D4.
  • Agree that Mansion tax and second house tax/ban should increase density and they already do.
  • Not sure about MTA as I don’t think newly married couples will live in more high density residence compared to singles or yet-to-get-married couples.
  • Mortgage Tax Relief might make urban housings more affordable but I think MTR to less Real Estate Bubble kinda reflects this.
  • Close Airport to higher density might be true. I’ll try doing some research. Obviously nobody lives in an airport (except for Tom Hanks :P) but it might actually boost developments in surrounding areas.
  • Farmer_perc to UD should make the list of causes shorter. But I decided not to do so because 1) Farmer_perc won’t display any influence arrow and 2) I have to add density modifiers to City Farms or Vertical Farms when they aren’t really going to considerably affect density.
  • Same as above for Young_perc to UD. Also, Young population doesn’t really change.
  • I too felt like there should be, at least, a catch-all-policy for development regulations just like the Labour Laws. I’ll consider this option after some playtest runs.
  • Also agreed that some kind of subsidies for high density or urban renewal would be nice to have. Will consider once the update made public.
  • Economies of Scale is a convincing argument for Private Healthcare/Schools boost under high UD. I can make these links dependent on State Healthcare/Schools but don’t think it will be needed. It should also be possible to modify income effects but want to avoid as I already have a separate mod that extensively modifies disposable income links. I guess I will just add boost to size of private ones and budget efficiency of public ones.
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-About the MTA. My reasoning behind it comes from an example from my home country which is dealing with a huge housing shortage. There are many causes for this shortage but one of them is that less people are getting into relationships and instead stay single for longer periods of time. This means that more houses are needed because less people live together which in turn decreases density. Incentivizing marriage with MTA will cause more people to live together which increases density.
-MTR is very complicated. On one side I would say that it makes housing more affordable and thus people now can afford bigger houses that take up more space which would decrease density. On the other side, it also increases demand for houses because, of course, lower price means higher demand. Which in turn could increase housing shortage, which in turn increases prices, which in turn could increase density. This might actually be too complicated to add to the mod but its up to you what you want to do with it.
-About the airports. Look up any major airport (for example LAX or JFK). Most of them are located inside or near a city and take up a gigantic amount of space. Closing them would free up this space and make room for more houses in the city and thus higher density.

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For anyone interested: the full list of current causes & effects of Urban Density


Source Equation Inertia Notes
Realestatebubble 0-(0.4*x) 16 part of cyclic forces
CoLUrbanDecay 0-(0.2*x) 8 part of cyclic forces
Homelessness 0-(0.12*x) 8 part of cyclic forces
GDP 0.4*(x^3) 32 to ensure long-term growth of UD
Wages -0.12+(0.24*x) 16 paired with CoL
CoLCostofLiving 0.12-(0.24*x) 12 paired with Wages
Population -0.15+(0.3*x) 2
Unemployment 0+(0.1*x) 8 might delete this
Immigration 0+(0.08*x) 4 immigrants will settle in cities imo
IllegalImmigration 0+(0.06*x) 4 immigrants will settle in cities imo
globaleconomy 0+(0.06*x) 4 bit arbitrary but I think this will give some ebb-and-flow
TechnologicalAdvantage 0+(0.16*x) 16 some jobs are concentrated in cities
Erasmus 0+(0.08*x) 12 undergraduates in cities
Pollution 0-(0.1*x) 16
Gridlock 0-(0.06*x) 12
ContagiousDisease 0-(0.16*x) 4
StreetGangs 0-(0.08*x) 8
InnerCityRiots 0-(0.08*x) 16
VigilanteMobs 0-(0.08*x) 8
ClassWarfare 0-(0.2*x) 16
RaceRiots 0-(0.08*x) 16
Ghettos 0-(0.12*x) 16
AgricultureSubsidies 0-(0.03*x) 16 other jobs are far away from cities
OilDrillingSubsidy 0-(0.04*x) 12 other jobs are far away from cities
OrganicSubsidy 0-(0.03*x) 16 other jobs are far away from cities
RareEarthRefinement 0-(0.03*x) 12 other jobs are far away from cities
RuralDevelopmentGrants 0-(0.12*x) 24 other jobs are far away from cities
TelecommutingInitiative 0-(0.02*x) 12
BusLanes 0+(0.04*x) 12 anti-car
CarTax 0+(0.04*x) 12 anti-car
CongestionCharging 0+(0.02*x) 12 anti-car
Limitorbancarsincities 0.06+(0.06*x) 24 anti-car
PetrolTax 0.05*(1-ElectricCarTransition)*x 12 anti-car
Punitivetaxonsuperstores 0+(0.02*x) 12 anti-car
RoadBuilding 0-(0.2*x) 24 pro-car
SateliteRoadPricing 0+(0.03*x) 12 anti-car
TollRoads 0+(0.04*x) 12 anti-car
BanSecondHomeOwnership 0+(0.08*x) 8 less waste of urban space
EmptyHomesTax 0+(0.08*x) 16 less waste of urban space
GatedCommunities 0-(0.04*x) 16 less sprawl
MansionTax 0+(0.02*x) 16
Gambling 0+(0.03*x) 12 some jobs are concentrated in cities
StemCells 0+(0.03*x) 12 some jobs are concentrated in cities
TechnologyColleges 0+(0.02*x) 12 undergraduates in cities
UniversityGrants 0+(0.06*x) 16 undergraduates in cities
Closeairportscompletely 0+(0.04) 16 less waste of urban space
_prereq_southkorea 0+(0.15*x) unique modifier for S.Korea
_prereq_tsunami 0+(0.06*x) unique modifier for Japan
_prereq_indigenous 0-(0.05*x) unique modifier for US/CA/AU


Target Equation Inertia Notes
Realestatebubble 4*(x*0.02)+1*x-CoLUrbanDensityPast part of cyclic forces
CoLUrbanDecay -5*(x-CoLUrbanDensityPast) part of cyclic forces
CoLCostofLiving -0.1+(0.2*x) my original intention
EnergyEfficiency -0.1+(0.2*x)
ElectricCarTransition -0.15+(x^2)*0.3 more infra needed for e-car so slower transition
CarUsage 0.15-(0.45*x) 6 less cars in compact cities
TrafficCongestion -0.045+(x^2)*0.4 but also less road capacity in compact cities (still less congestion in total)
BusUsage -0.12+(0.24*x) and more public transit
RailUsage -0.05+(x^2)*0.2 and more public transit
CrimeRate 0.12*(x^2) 4 more crime opportunities but will also get efficient tools
ViolentCrimeRate 0.12*(x^2) 6 more crime opportunities but will also get efficient tools
MentalHealth -0.08*(x^2) a bit more health problems
HealthcareDemand 0.06*(x^2) 12 a bit more health problems but private healthcare alone will be able to cover this
PrivateHealthcare -0.04+(x^2)*0.16 4 economies of scale
PrivateHousing -0.04+(x^2)*0.16 4 economies of scale
PrivateSchools -0.04+(x^2)*0.16 4 economies of scale
Environmentalist -0.15+(0.3*x) they want compact cities
Commuter -0.2*(x^2) represents more needs from commuters
Commuter_freq 0.16*(x^2) 4
Farmers 0.12-(0.24*x) rural decline
Farmers_freq 0.05-(x^2)*0.2 4 rural decline
Farmers_income -0.1*(x^3) rural decline
StateHealthService_cost 0.15-(0.3*x) 6 less service cost
StateSchools_cost 0.15-(0.3*x) 6 less service cost
StateRail_cost 0.07-(0.14*x) 6 less infra cost
StateEnergy_cost 0.07-(0.14*x) 6 less infra cost
Monorail_cost 0.07-(0.14*x) 6 less infra cost
SocialCare_cost 0.08-(0.16*x) 6 less service cost
StateHousing_cost 0.4*(x^3) I find state housing bit OP and it sounds reasonable to take more budget if cities are densely populated
StateWater_cost 0.07-(0.14*x) 6 less infra cost
StateTelecoms_cost 0.07-(0.14*x) 6 less infra cost
PoliceForce_cost 0.12-(0.24*x) 6 more crime opportunities but will also get efficient tools
BusSubsidies_cost 0.07-(0.14*x) 6 less service cost
Recycling_cost 0.07-(0.14*x) 6 less service cost
StatePostService_cost 0.07-(0.14*x) 6 less service cost
SmartMeterProgram_cost 0.1-(0.2*x) 6 less infra cost
watermeters_cost 0.1-(0.2*x) 6 less infra cost
CommunityPolicing_cost -0.1+(0.2*x) 6 to be fair I don’t really like community policing because it’s so OP and it sounds plausible that it’s more burdening to deal with populated communities

+I’m starting to feel like benefits of close proximity between the residents and their needs (work, shopping, etc) should be represented somehow but not sure how. any input would be really appreciated.

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Maybe we could try to simulate the flow of ideas that highly dense cities have. Denser cities could be hotbeds of innovation and boost technology and education, as there would be more educated professionals in one area. This would also boost productivity, which I think makes sense: in almost all areas, the cities are the main drivers of economic growth.

After googling I found this study from the London School of Economics. It says that highly dense cities are better for the economy so there’s an argument that higher urban density could directly boost the GDP. However, it notes that cities have more expensive housing which leads to inequality, which you have also mentioned, though a direct lever on inequality could also be used. I personally believe as well that urbanisation should improve the environment directly due to humanity’s footprint shrinking.

Perhaps another suggestion, from me? Maybe higher urbanisation should increase the rate of liberalism. In most areas major cities lean further to the left than rural areas, but this would be a long term shift.

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Nice suggestions. Here are my thoughts:

  • High Urban Density leading to higher Productivity or GDP sounds plausible (I’d prefer Productivity boost though). I’ll take a close look at it.
  • I made high UD lead to higher Cost of Living, which could result higher Poverty. Plus to that, high UD makes a country more vulnerable to Real Estate Bubble which can massively (-22% at max) undermine Equality. So I think driving UD up without proper housing policies will damage Equality.
  • Right, compact cities will, at least, take less amount of land and thus leave more natural habitats undamaged, which isn’t reflected just by higher Energy Efficiency. I’ll add a link boosting Environment under high UD.
  • I see that urban constituencies tend to be more liberal but I want to avoid that because Liberalism is already kinda strong.
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I honestly don’t see why UD would lead to higher Cost of Living. I would even argue the opposite because high density means there is more supply of housing resulting in lower prices. Or don’t you think?

edit: thats also why I added cost of housing as a different simulation (blue bubble) in my mod concept.

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To be fair, I think you may be right, especially in the long term. But I have decided to implement in this way because…

  • the reason I’ve started designing this was to implement unique CoL modifiers for S.Korea and Japan, which have high population density
  • the fact cities don’t continuously grow as dense as possible themselves when unchecked suggests that sprawling out is the path of least resistance, which means lower costs in this case
  • some research I’ve done recent days suggested that higher urban density tends to lead to higher cost of living
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Second Iteration of Urban Density & Urban Decay

What I’ve done

  • Re-wrote descriptions
  • Added negative impacts to Urban Decay
  • Adjusted some numbers for balance
  • First full playtest run


Urban Density
Urban Density is a general measure of urban areas indicating the intensity per unit area of not only people but also jobs, housing, amenities, and social activities. Though cities are, by definition, dense settlements, their density can vary as there are numerous factors like urban sprawl. It is desirable to keep urban density stable since housing supply often can’t cope with fluctuating demand in time. A drastic change in demand can lead to a crisis such as real estate bubble or urban decay.

Urban Decay
With the urban environment becoming increasingly poor to its inhabitants, population flights to the suburbs are at rise. This phenomenon not only means more suburb expansion but also more slum formation in cities. It can end up forming areas of concentrated poverty, further amplifying its negative impacts to social fabric.


was like this at turn 0 (click to expand)

another turn-0 screenshot showing Urban Decay

Findings and Thoughts

  • Sensitivity of rise/decline detectors seems fine in my eyes. But I might make decline detector a bit less sensitive since I had understanding of how they work. It might feel complicated or even punishing for players.
  • Cost of Living and Urban Density seem to have made Australia mission much more difficult. They now start with 9 Law & Order problems (Internet Crime, Inner City Riots, Armed Robbery, Ghettos, Antisocial Behaviors, Organized Crime, Street Gangs, Alcoholism, and Vigilante Mobs). 4 out of 9 (Ghettos[+40%], Street Gangs[+30%], Antisocial Behavior[+20%], Inner City Riots[+20%]) are directly instigated by Urban Decay. I guess some of the others like Vigilante Mobs, Internet Crime, or Armed Robbery has been boosted indirectly. Though I was able to fix all of these, it seems rather too extreme. Might tone down some negative impacts such as crime.
  • Thankfully, other countries don’t experience such an extreme crisis under Urban Decay. I assume that Food Crisis (which exists at turn zero in the Australia mission) was a defining factor.
  • It took roughly 50 turns to max Urban Density in Australia. But I’d take this result with a pinch of salt since 1) Urban Density started its rebound at 13% (thanks to all these law & order problems…), 2) I’ve chosen to accelerate urban growth by giving up dealing with the bubble, and 3) major anti-car policies (including limit car) have been adopted while intentionally avoiding some good policies which are bad for urban density. I’d also mention that I naturally have full knowledge on how modded things work so players might struggle with bubble & decay.
  • While I did give up completely solving the Real Estate Bubble, I’ve implemented several anti-bubble measures including strong state housing, empty home tax, mansion tax, and mortgage tax relief. It was rather surprising that the bubble didn’t stop until the density growth slowed down at 90%, despite all these efforts.
  • Since I was trying to maximize Urban Density, I didn’t have a chance to trigger Urban Decay again. To be fair, I don’t think it will go down again from 90+. I might have faced it again if I decided not to give additional boosts to urban density so that I can avoid it.
  • Bubble was rather quick to get triggered once I escaped urban decay. Not sure whether I should add inertia to bubble as doing so will not only mean delayed trigger but also delayed end. I’ll try adding an inertia of 3 turns to UD-Bubble link next time.

List of Causes & Effects of Urban Decay

Source Equation Inertia Note
_default_ 0.2
CoLUrbanDensity -5*(x-CoLUrbanDensityPast) part of cyclic forces
Uncompetitive Economy 0.2+(0.1*x) “rust belt”
PovertyRate 0+(0.1*x) for a bit of flavor
Equality 0.12*(1-x)^6 16 for a bit of flavor

Target Equation Inertia Note
CoLUrbanDensity 0-(0.2*x) 8 part of cyclic forces
Realestatebubble 0-(0.16*x) to prevent having both of bubble & decay
Ghettos 0.2+(0.2*x) 8 iconic result of decay
_LowIncome 0-(0.07*x) 8 concentrated poverty
Poor 0-(0.2*x) concentrated poverty
AlcoholConsumption 0.1*(x^2) 8 concentrated poverty
CrimeRate 0.3*(x^2) 8 concentrated poverty
Education 0-(0.06*x) 16 concentrated poverty
Equality -0.16*(x^2) 8 added for flavor but seems bit too punishing?
ViolentCrimeRate 0.07*(x^2) 12 concentrated poverty
RacialTension 0+(0.14*x) 16 concentrated poverty
StreetGangs 0+(0.3*x) 4 concentrated poverty
AntisocialBehaviour 0+(0.2*x) 4 thought this fit well but unsure
DrugAddiction 0+(0.15*x) 12 thought this fit well but unsure
InnerCityRiots 0+(0.2*x) 12 starting point of riots
ClassWarfare 0+(0.07*x) 12 starting point of riots
RaceRiots 0+(0.3*x) 12 starting point of riots
LudditeRiots 0+(0.2*x) 12 starting point of riots

as you can notice from that list above, I haven’t done a deep research on urban decay/decline to be honest. :sweat: I just assumed it as concentration of poverty in confined areas. Something that doesn’t have significant impact on national average but can seriously mess a small cross section of society. Therefore, plus to some common impressions on slum areas, I’ve brought lots of effects from poverty.

any feedback on Urban Decay would be greatly appreciated.

+just an idea came to mind. what do you think about a new positive situation: Pedestrian City (or Walkable City)? Super high density & low car usage. not sure what to add as benefits. not going to add right away just an idea on my note.


Thankfully it doesn’t look like my mods don’t have any conflict with the new Voting Systems DLC. I did another test run - this time on South Korea, where I added +15% Urban Density modifier. There also have been some changes but mostly balancing so that Australia or other countries don’t start with serious situations. AUS will now have only 5 law & order problems at turn 0!

Findings & Thoughts:

  • S.Korea started with Urban Decay. actually, only some countries like US, UK, ES, FR don’t have it on turn 0. (might differ for other players as I use all my mods including Labor Income Share, which can’t be published on workshop)
  • It already had kinda high Urban Density thanks to the modifier & despite having Urban Decay in effect. So it didn’t take long (30s turns) for UD to reach 100% from 56%. I didn’t even put much efforts to boost it. Just kept GDP high and nurtured high-tech sectors. I assume that +15% modifier is actually quite huge but it could make sense as SK has high pop density and very strong anti-sprawl green belt on its metropolitan area.
  • This time I had activated most anti-bubble measure in advance to see if I can actually prevent it while maintaining urbanization trend. The result was very safe & strong 2%p/turn growth in density without bubble. But I got some warnings about it.
  • Density growth without anti-car policies gave me occasional congestion spikes. This is since high density doesn’t really contribute to lower congestion. I don’t think this to be punishing though.

I guess I could push an update tomorrow? no glaring issue on my eyes.

Published Urban Density as a sub-mod of Cost of Living!


Cool, I’ll check it out soon and let you know what I think!

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Your mods are translated in all language?

Just English & Korean.

not italian?

I can’t speak it. could add machine-translated texts though.

Hello! I have been trying to find some mods to play in the game lately, and I found your mods to be very interesting to try out, but I didn’t own the steam version of the game to subscribe them on the workshop. Would you mind having a direct download links for all of your mods please? That would help me a lot!