Holy smokes, this is an insanely successful city! I'm in awe.
I think an answer to one of your questions is simple math:
View attachment 1272044
.05%
I didn't realize how huge your city is. It may be that the game simply can't show a value this small as a percentage ... that doesn't explain, however, why the absolute value of unhoused cims in your population screen shows zero.
The monthly dump question also makes sense now. I have seen that. Mine always seems to recover somewhat quickly, although sometimes it can be a little bit pokey. I'm guessing because my city is half the size of yours it hasn't been a problem that I've really felt yet. Your city is immense, so such a huge volume of seniors passing away may impact your demand bars differently than in a city of only 190K.
I'm not sure how to correct the demand issue. I often try to induce demand by lowering my tax rates, but yours are already pretty low. I also play with an eagle eye on the demand bars, so that I can keep them balanced as a I play (a conditioned habit from SimCity 2000).
I'm not sure how you fix the monthly dead cim dump w/o attempting to expand the lower educated end of your economy. The better educated end of your economy is stable. My guess is most of those cims dying are retired, so there are no higher paying jobs to fill that inbound cims could occupy.
I understand the dilemma with respect to residential demand bars. With the anniversary patch, it does seem to me that the commercial demand bar is far more sensitive to residential demand for consumer goods. So it makes sense that when your residential demand crashes your consumer demand would as well. I would like to think that if I have a surplus of jobs and homes available, That would entice younger workers.
Also, what kinds of residences are being vacated by those passed away cims? A younger worker may not have the wealth to afford rent in a high-density apartment. Maybe you have a mismatch between education levels of the open jobs and education levels necessary to be able to afford a higher rent apartment?
I think this may be at last part of the issue ...
your highest levels of unemployment are at the uneducated and poorly educated end of the labor pool, while the vast majority of unfilled jobs are at the top end of the labor market. Any incoming uneducated and poorly educated workers are not hirable at those higher level jobs. And they also probably can't afford the rent for those apartments either. So they either enter the city, become unhoused, and then leave quickly -- or they don't enter the city at all.
Ironically, you have very few unhoused cims and you also have very few commuters, which I read to mean that the uneducated and poorly educated workers
are finding affordable housing in your city.
Also, you have about 3.5K unfilled jobs in this city. Is that a result of the monthly death wave or is that systemic to your economy? I'm not sure, but I've always assumed that the jobs market also affects RICO demand. In other words, the game signals you to build more commercial, for example, when there are more consumers--but ALSO when there is a surplus of poorly educated and educated workers.
As I was investigating, this happened in Sept 2038:
All of a sudden you have several thousand newly unhoused workers at the higher educated end of your economy.
I wonder ... if you start a new city in another location on the map, then you can establish it as a district and that would help you keep track of its demographics. My inclination is to say you simultaneously need high density housing for those unhoused cims. My guess is your game removes them quickly enough you may not be aware of the phenomenon. New cims will come in to fill office jobs, but they can't find homes because elderly cims have snatched them up--so they become homeless and then quickly leave (but I'm not sure why they wouldn't then become commuters).
On the other end, you need to expand your industrial and low density commercial sectors to provide jobs for those cims at the lower end of the education spectrum.
Maybe a bunch of high density affordable housing projects, adjacent more extractor enterprises and industrial parks? That would provide homes for cims at all education levels
Lastly--and I'm loath to recommend this because it can create a lot of volatility in a stable system--but I often lower my taxes in order to induce demand. You have a lot of money in the bank. Maybe you run at a deficit for a little while in order to induce demand for the bars that won't bounce back?
Another thought ... you could build and zone that second city knowing it won't immediately zone in ... and then just let the game run. If I'm understanding everything correctly, there will be some moments when demand briefly returns ... if you have everything pre-zoned then buildings will spawn during those moments when the demand bars pop back up. That might be enough to get the apple cart rolling again. If you zone out a new city first, THEN drop your tax rates to induce demand, you might be able to jump start the expansion process.
[I suggest that knowing that your city is already at 450K population, so I can't imagine how your computer handles all this.]
Also ... I've been trying to live without mods as much as possible, but there is a demand mod available for CS2:
https://mods.paradoxplaza.com/mods/86944/Windows
over 10K subscribers and 140 thumbs-up ...
probably safe to use, but read the forum chat.