Rather than raising the 'cash rate' which increases the cost of all borrowing, the RBA should have the power to levy an extra charge (like a GST) on all lending for purposes which it wants to quell. Eg if house prices are raging in a certain city, but not elsewhere, increase the cost of borrowing for existing homes only in that a city. This makes new homes relatively less expensive, encouraging supply. This approach can be extended to all manner of borrowing where you want to target a specific sector and/or region