A Platts assessment is the product of a market survey and the application of strict methodological rules to determine the repeatable tradable price range for a commodity during the assessed period. Assessment typically aims to zero in on these typical transactable levels by discarding unrepresentative market information (out-of-market bids, offers and transactions), and the process differs in this respect from indexation, which is an inclusive process, averaging all available market information. Platts produces indexes in highly liquid markets, for example North American natural gas; and assessments in illiquid markets, such as those for physical oil. Platts assessments typically are published as a low-high range for each instrument.