Opec’s non-decision over output at its 4 December meeting has been interpreted by the organization’s own members, and markets, as a production free-for-all. Oil prices have tanked. Brent was trading below $39/B, the lowest level in almost seven years, as MEES went to press. Gulf benchmark Oman, which is more typical of Opec’s core Gulf members’ crude exports, fell to just $35/B on 10 December.

Opec members can now expect to take in a mere $514bn in collective revenue...