Hon GRANT ROBERTSON: The member would be wise to think about what non-tradable inflation is and what domestic inflation is; we have a thing called CPI which includes tradables and non-tradables. Consistently in New Zealand's history, non-tradables have exceeded tradables. We've had a period where that's been in reverse but it's now going back the other way. The non-tradable inflation is severely influenced by global factors—for example, housing, which is regarded as a non-tradable. One of the biggest components of the increase in housing costs in the last quarter was building materials, which is caused by the supply chain constraints from overseas. 