Turning a market into a commodity market helps make it really thick, because any buyer can buy from any seller, and any seller can sell to any buyer. At the same time, it also helps the market deal with one of the main sources of congestion in matching markets, since in a commodity market each offer to sell can be made to all buyers, and each offer to buy can be made to all sellers. So unlike in the market for jobs, or for houses, no one has to wait for an offer to be made to him personally;
