The good CDR was kind enough to link to me in his post Yo,ho, ho, .... thar'ye be! in which he refers to an article in The Economist in which there is an handy dandy "chart of piracy." This particular article relies on International Maritime Bureau statistics to which I frequently refer in some of my "pirate" posts. However, it would be a mistake to think that every incident referred to by the IMB involves a pirate crew laying along an intended victim and doing piracy the old fashioned way. While that has happened, especially recently in international waters off Somalia, most IMB "piracy" is not like that at all, as I attempted to explain in a comment to Salamander's post:
Thanks for the link, CDR. It should be repeated, as I often do at my place, that those IMB figures on which the article is based include thieves climbing up anchor chains while ships are anchored in harbors and roadsteads (this is especially true in Bangladeshi waters) or suspicious approaches as reported to the IMB. The vast majority of the incidents occur in the the territorial waters of some state or another and do not constitute "piracy" as that term is defined in UNCLOS which requires the action to occur on the "high seas."See also here.
Given the rather liberal interpretation of piracy used by the IMB, I am somewhat surprised they don't include theft from ships moored to piers which would certainly inflate their numbers. I guess they had to draw the line some place...
Worth noting in the trend lines is the big decrease in Malacca Strait "piracy" since a multinational force from the strait's littoral countries began operations.
Somali, of course, has no effective law enforcement and there is a pretty nifty ransom scam going on but again, the addition of escorts for UN World Food Program shipping has reduced the capture of the ships involved in that business down to zero and the pirates have begun seeking unescorted and minimally manned ships in other areas. Probably a simple convoy system, even without escorts, would help slow that business down.
Nigeria is having rebel trouble.