1. A method of managing trading, comprising: in a market for a particular type of instrument, receiving trading orders from a plurality of traders, each trading order having an associated price; placing each of the received trading orders on a trading exchange such that the trading orders may be executed, including placing each of the received trading orders in one of a plurality of trading order stacks; determining whether the price of a particular trading order differs from at least one comparison price by more than a threshold value; and if it is determined that the price of the particular trading order differs from the at least one comparison price by more than the threshold value, restricting the promotion of the particular trading order within its respective trading order stack.