The decline in Somali piracy (which, according to a recent World Bank report, may at its peak have cost the world up to $18 billion a year in extra shipping expenses and lost trade) is partly the result of increasingly sophisticated co-ordination by international naval task-forces. Shipping companies are also making their vessels harder to attack thanks to a range of defensive measures, such as razor wire around decks, high-pressure hoses and maintaining speeds that make boarding hazardous. Armed security guards on many of the ships transiting pirate-infested waters have helped too.But the pirates could still make a comeback. The cost of deterring them is high. Shipping companies may lower their guard if they think the threat has passed, and patrolling naval forces could be needed elsewhere. And although Somali piracy has faded, west Africa has seen a surge in attacks on ships passing through the Gulf of Guinea.

Tom Patterson, a maritime security expert at Control Risks, a consultancy, says these pirates, who largely come from militant groups in the Niger Delta, have a different business model to their Somali counterparts. They tend to hold ships for about two to five days, removing as much of their cargo as possible (usually gas oil) and then auctioning it to the highest bidder. Hostages are taken if potentially valuable. This week five Poles and Russians, held since April 25th when pirates attacked the German-operated City of Xiamen container ship off Nigeria’s coast, were released, doubtless after a ransom payment.

International naval forces are unlikely to intervene. Nigeria has a decent navy of its own which claims to be upping its efforts to contain piracy. But foreign diplomats believe that some military officials turn a blind eye to thefts in return for a share of the spoils

Hijackings on the high seas: Westward Ho!, Economist, May 18, 2013, at 67