Houses are unique and have irreducible transaction costs which makes the market for them very inefficient and slow relative to a commodity. For one example, if you are in the market for a 3-bedroom house with a garage, the market is already segmented much more narrowly than can be the case in an efficient market like that for a commodity. If you have to move into one as soon as possible for a new job, and you know closing will take a minimum of 3 months, the market for your prospective houses is going to be extremely small without even factoring in other distinctive characteristics like driving distance and schools. 4% of the aggregate market may represent 25-30% of your “market” nonetheless.