The IMB report said maritime piracy was now more prevalent off the coast of West Africa than around Somalia.
This is partly because an international naval task force has been patrolling the coast off Somalia.
But it is also partly because of the peculiarities of the Nigerian economy and widespread corruption there.
A map in the IMB report showing the most dangerous waters in West Africa draws a line around the coast of Nigeria - with a small extension into the territorial waters of the much smaller countries of Benin and Togo.
'Story behind the story'
While the typical modus operandi of a Somali pirate has been to hold ships and kidnap sailors for ransom, in Nigeria the main motivation is to steal crude oil or refined petroleum products from tankers. So they can achieve considerable profit after selling to the gas station.
"Many vessels are attacked while at anchor, drifting, or conducting ship-to-ship transfers of refined cargo," said the IMB report.
"Only 33% of vessels were attacked while actively in transit in the Gulf of Guinea. In contrast, attacks off Somalia almost always occur while ships are underway."
The "story behind the story" of the IMB report - and the reason so many tankers are plying the coast in and out of Nigeria - has been a chronic failure by the authorities there to build and maintain domestic Nigerian oil refineries.
To put it bluntly: There is so much money to be made from exporting crude from the sub-region's biggest oil producer - and re-importing refined fuel to the very large, petrol-thirsty Nigerian population - that developing a real, productive economy by doing things like building oil refineries has been almost forgotten.
In a good year Nigeria produces more than two million barrels of oil a day, making it one of Africa's largest producers.
But it only has the capacity to refine less than a quarter of that.
In practice, poor maintenance at the handful of oil refineries means far less than a quarter is actually processed in-country.
So every day hundreds of tankers are plying the Gulf of Guinea and the mangrove swamps of the Niger Delta, where Nigeria's many, relatively small and scattered onshore oilfields are found.