Oil ministers from Saudi Arabia, Russia, Venezuela and Qatar announced on Tuesday an agreement to freeze their oil output levels provided other major producers follow suit. The deal would freeze Saudi and Russian production at the record rates reported in January and is unlikely to be accepted by Iran in its current form since the country escaped from sanctions only last month. The agreement is provisional (depending on adherence from other oil producers) and unambitious (freezing rather than cutting production), which has led some commentators to dismiss its importance. But experience suggests production agreements are normally reached in stages, often after several earlier attempts have failed or been only […]