When someone rents in a new building, they may be vacating an old. While there are laws in PA around vacancy decontrol (rent raised at renewal of lease), we do not have any around vacancy control (rent can only be raised x amount for the new tenant). Without that any landlord will of course seek the best rent they can, often a substantial jump and thus a decrease in supply of lower rate rentals. This can be addressed long term with ample supply, both public and private. However in addition to increasing supply, we should be looking at some sort of price control.