Derivative contracts. such as futures and short options, require brokers (i.e., the clearing members of an exchanges clearing house) and investors/speculators to post initial margin. Which is usually a fixed dollar amount per contract and represents a very small percent of the overall value. Futures and option contracts are agreements that are directly between a clearing member (e.g., broker) and the clearing house. As a result. there are separate margin requirements for the broker relative to the clearinghouse and for the customer relative to the clearing house. The exchange sets minimum customer margin requirements. but brokers are allowed to charge customers amounts in excess of this minimum. The minimum exchange set margin requirement depends on factors such as price volatility (e.g.. worst daily movement) and general market liquidity.