Immigration is about real estate, debt and interest. An expanding population keeps property prices high, all banking is secured on property and property price increases mean they can lend more. The opposite would literally cost millions every day and if not managed correctly ultimately lead to crashes. The perfect balance is enough for housing to remain scarce but also allow for a steady increase in new builds to expand their portfolio. The immigration flow is turned on and off accordingly. (((They))) don't think any further than this.