If the population is dropping because lower income workers are leaving, average rents will go up as occupancy goes down.
Think of it this way - you probably won’t move to a cheaper house just because one becomes available- but you might move to a nicer one of the financials worked.
Working class people are also more likely to have multiple roommates. So if one roommate leaves, maybe the others can no longer afford the full rent so they move too, now the landlord white washes the walls and jacks rent and it goes to a single high income individual who can afford three bedrooms themselves in manhattan.
Also, rents numbers are usually not given after adjusting for inflation. It makes breaking record a phenomenon you’d expect, similarly how Hollywood keeps constantly breaking its blockbuster records.
Think of it this way - you probably won’t move to a cheaper house just because one becomes available- but you might move to a nicer one of the financials worked.