plummeting residential demand

[mistershnerples 0]

So I think a lot of us have experienced this problem. For me, it's happened with the last three major cities I've built. So my residential populations seem to always reach 900,000, and then demand just shoots down, with thousands leaving in droves. I tried adding more industry in the neighboring city and in the city itself, but to no avail. I'm wondering if there is an issue or if anyone has any advice to deal with this issue.

On a separate topic though, I recently added the Air Purification Park from STEX (which is amazing), and the residential demand bar is all the way down, but my population level seems to be level or barely diminishing. I'm wondering if that is a side effect of not having pollution all over and Sim want to stay in the city, despite low demand? Thanks!

[tungston 19]

Air pollution doesn't have any affect on low wealth, and very little on medium wealth, high wealth desirability goes down as the pollution goes up.