Historically, governments have intervened in the agriculture sector more than in other sectors. Agriculture was always covered by the General Agreement on Tariffs and Trade, which entered into force in 1948. But numerous exemptions meant agricultural trade escaped most of the disciplines that applied more generally to trade in industrial products. The result was the widespread use of measures that obstructed imports — import bans, limits on quantities that could be imported (quotas), high import duties, import duties whose rates varied and so created market uncertainty, minimum import prices, and various impediments not related to tariffs such as regulations and the activities of state trading enterprises. Major agricultural products such as cereals, meat, dairy, sugar and a range of fruits and vegetables faced trade barriers on a scale unseen in the rest of merchandise trade.