Algeria has a reputation for unreliable and misleading energy statistics. Its favorite metric is the ‘ton of oil equivalent,’ and for gas the headline numbers are typically for wellhead output – up to half of which is subsequently reinjected or flared.

But, whisper it, the gas numbers that Algiers has been reporting to the Riyadh-based Joint Oil Data Organization seem credible. Those for past years tally with data from other sources – namely Spanish and Italian...