Source: ICC International Maritime Bureau. Encoding of piracy events by William Moreto.
As long as there has been trade, there has been an incentive to plunder the valuable commodities transiting along long distance maritime trade routes. The conventional response was for ships to travel in convoys, escorted by military ships if the trade was of sizable value, with merchant ships commonly being armed. As most navigation was taking place along the coasts, this presented ample opportunities for merchant ships to be boarded by pirates. The evolution of maritime piracy and its hot spots marks the ebbs and flows of global trade. Prior to the 15th century, most piracy was taking place along the routes leading to East and Southeast Asia from the Middle East. The colonial era with the Spanish conquest of Latin America and the repatriation of the wealth of the colonies incited piracy in the Caribbean from the 16 to the 19 centuries. The emergence of Great Britain as a global maritime power led to a substantial decline in piracy as the global interests of the British Empire were being actively protected by its navy. By the 20th century, piracy became a marginal activity as ships became bigger and faster (more difficult to board), most of the commercial navigation taking place in the high seas (more difficult to spot and intercept) and as the cargo being carried shifted to bulk or break bulk, which could no longer be easily hauled away.
The surge in global trade in the second half of the 20th century created an environment where piracy appears to be on the rise. Shipping lines are forced to pass through constrained areas, chokepoints, namely straits such as Malacca and Bab el Mandab along the heavily used Asia-Europe maritime routes, which makes the interception of ships more feasible within a delimited area. Poverty and political instability are also linked with piracy as on one side piracy becomes a source of revenue and on the other there are limited national institutions and means available to deter piracy. In such a vacuum, loose but well organized piracy activities have emerged. Both Somalia and Yemen can be considered as dysfunctional states that are unfortunately located on both sides of the Gulf of Aden where shipping routes converges on their way to the Red Sea and the Suez Canal. As the above map underline, they represent the largest concentration of piracy activities in the world, along with the Strait of Malacca, the South China Sea and the Gulf of Guinea (mostly Nigeria). A troubling pattern that has emerged since 2008 is the growing distance from the coast piracy acts occur at. This is particularly the case off the Eastern African coast and implies the usage of larger re-supply ships serving as logistical platforms for high seas piracy operations.
Piracy tends to take place in international waters, which creates a problem of jurisdiction. The most common piracy strategies involve boarding the ship to steal from the crew or the passengers, abducting the crew and/or the ship and ask for a ransom from the shipping company (which is more than often paid) and stealing the cargo (or sometimes even the whole ship) and selling it on the black market.
Piracy is well known to take place on the high seas, but a significant share of the acts that are considered as piracy take place while a ship is docked at a port, where there is an easier opportunity to board. This occurs at terminals in developing countries where security is more lax or where port security officials can be bribed.