Hon Dr DAVID CLARK: Market concentration has, indeed, been raised as a concern. We know there are two concrete firms that supply about 85 percent of the sector. We know that there are three glass wall insulation firms that control about 85 percent of the sector—one plasterboard manufacturing firm that controls about 94 percent of the market. There are rebates and loyalty schemes operated by some firms, and I believe it's in the public interest to have a look into these matters.