The empirical evidence from around the world is as clear as it gets: In the long run, housing costs are mostly determined by the severity of planning restrictions (see here, pp. 17-19). Those who are emotionally attached to the British planning system try their best not to see this connection by looking for explanations, however implausible, outside of the planning system. What they do not realise is that most of the research tests alternative explanations, and carefully controls for a wide range of other potential factors. But the bottom line is that other factors, while not irrelevant, are ultimately sideshows when looking at a sufficiently long period. The first and foremost reason why housing is so expensive in the UK is that the planning system does not allow enough homes to be built. We only need to look at the number of dwellings completed over the past thirty years, and compare it to any other country for which data is available (p. 14).