Given the information asymmetry between buyer and seller, the latter has an incentive to cheat by providing goods of lower quality or in smaller quantity than agreed. Of course, the buyers will eventually notice the deceit and stay away from such a market. The ancient Greeks found a clever solution to this problem: they established public institutions to improve and maintain market efficiency.
5 The city-state provided standardised weights and measures that merchants were obliged to use. For instance, the agora featured a stone table, the "sekoma"; it had several cavities which were used to measure different volumes. Special magistrates, the "agoranomoi", examined the quality of products and watched over the proper conduct of transactions.