This discussion is intended as a continuation of a comment on variable flat size.

The original comments were from me, 11 September:

Originally posted by spamf:

I have the same issue as @ravzir. For some buildings, the number of households (significantly) decreases when these buildings level up. This is very annoying, because the total city population reduces over time and drops noticeably when many buildings level up the same time, e.g. after placing a hospital or park nearby, then causing issues with worker availability. @algernon I have not found anything in the documentation (the Wiki page). If calculations were based on the physical size of the building, then the number of households must not change as the physical size doesn't change with building level, right?

and

Originally posted by spamf:

I have just discovered that it is actually intended that the number of households changes with building level. It is because both empty area and area per unit change in the population calculation pack. Sorry for missing that. Still I personally find this annoying since a manually plopped building does not physically change, so the number of flats should be constant. But then you can adapt this to your own needs.

algernon replied shortly after:

Originally posted by algernon:

@spamf The trend observed in the real world is that as buildings 'level up' (i.e. gentrify/are rennovated to higher standards) there are fewer apartments within the same footprint (a combination of larger individual apartments and greater size-per-resident of shared and utility floorspace), even when the building size and exterior remain unchanged.

In some municipalities, this is a significant trend with material impacts on city planning outcomes.

This is what the default calculations are intended to reflect (if anything, the default calculations understate the observed real-world behaviour, as a deliberate choice to err on the side of conservatism).

And yes, as with everything else in the mod, that can be changed if you wish.

I would like to continue and deepen the discussion, but the number of characters for a comment is limited. So here is my answer in the form of a discussion.

@algernon Thanks for your description. While I understand the general logic behind it, I have rarely, if ever, seen it in real life. Of course, the building may be renovated to higher standards, but once it is built, the number of flats usually does not change, at least not that significantly.

Now, in C:S you could have a building grown or plopped. If it is grown, it changes its shape when it levels up and usually to a larger variant, which then provides more flats/households. Increasing empty area and area per unit counteracts this. Ideally, the total population does not change. This is probably quite realistic if the building level only represents wealth. And this is what is indeed seen sometimes: smaller/older buildings getting demolished to make room for larger/newer buildings, which usually have larger flat sizes these days. But for buildings that are manually plopped, these are usually not changed anymore and are also chosen in such a way that they correspond to the existing or expected level already at the point of plopping. Changing the number of flats as these buildings level up is fairly unrealistic and also quite annoying since the population then significantly drops over time.

The general problem I have with this logic is, that in C:S the building level is not only about wealth, but also about size. And the logic changes the specific flat size, whereas in real life it is not the specific but the average flat size that matters. And the average flat size has indeed increased over the years, changing the way new buildings are built and look. But this only applies to new buildings; for a house built in, for example, the 1980s the size of its flats is still the same, regardless of whether the property was renovated or the land value went up.

In my view, this logic tries to map a something in a significantly shortened period of time and oversimplified, which is in itself a development over several generations and is essentially influenced by the prosperity of a society: average flat size. For me, empty area and area per unit are thus constant values which should not change with building level, but if at all then only with time. Thankfully you have made this customisable and also implemented it very sensibly (!), so that I can now keep the values constant with my on calculation pack.