Please see below figures for piracy and armed robbery incidents as reported to the IMB Piracy Reporting Centre in 2012You might note that the IMB definition of piracy, while quite valid, is broader from that of the definition in the UNCLOS (piracy occurs on the "high seas"), which makes the IMB definition more inclusive of activity in the national waters of many states.
Worldwide Incidents: updated on 31 Jan 2012:
Total Attacks Worldwide: 37
Total Hijackings Worldwide: 2
Incidents Reported for Somalia:
Total Incidents: 13
Total Hostages: 28
Current vessels held by Somali pirates:
Vessels: 10 Hostages: 159
This has the effect of increasing the number of worldwide attacks in the IMB statistics. To clarify, by far the largest number of attempted and successful "on the high seas" piracy attacks occur in the Indian Ocean and are the handiwork of Somali pirates.
You will note that the IMB has added "armed robbery incidents" (see highlighted section) to its description of its numbers. This is correct, as some activities that occur in national waters that would constitute piracy if they were committed on the high seas are classified as "sea robbery" because of their location.
Also, the IMB includes robberies that occur on ships at anchor in its numbers. Again, quite proper, but something you should be aware of in looking at the numbers. Highlight added by me.