Generally speaking, an anti-dumping investigation usually develops along the following steps: domestic producer(s) make(s) a request to the relevant authority to initiate an anti-dumping investigation. Then investigation to the foreign producer is conducted to determine if the allegation is valid. It uses questionnaires completed by the interested parties to compare the foreign producer's (or producers') export price to the normal value (the price in the exporter's domestic market, the price charged by the exporter in another country, or a calculation based on the combination of the exporter's production costs, other expenses and normal profit margins). If the foreign producer's export price is lower than the normal price and the investigating body proves a causal link between the alleged dumping and the injury suffered by the domestic industry, it comes to a conclusion that the foreign producer is dumping its products. According to Article VI of GATT, dumping investigations shall, except in special circumstances, be concluded within one year, and in no case more than 18 months after initiation. Anti-dumping measures must expire five years after the date of imposition, unless a review shows that ending the measure would lead to injury.