The migration of drug trafficking operations is often put down to the"balloon effect," a theory touted by many academics and proponents of drug policy change that states anti-narcotics efforts and increased interdiction in one area leads criminals to shift operations to another, rather than having the intended impact of cutting profits and increasing costs to drug traffickers.

The essay "The Mobility of Drug Trafficking," included in a new London School of Economics (LSE) report (pdf) on the failures of current drug policy, finds that in regards to cocaine routes, this metaphor is an over-simplification.

University of Maryland professor Peter Reuter argues that a lack of reliable data regarding drug flow along one path or intensity of interdiction efforts in a given country makes it extremely difficult to determine the extent to which supply intervention is responsible for these shifts.

Determining causality is also complicated by the numerous other factors that impact smuggling costs, and in turn route choices. A country's appeal as a transshipment point can be related to its proximity to a producer or consumer country, shared culture and language with traffickers, and corruption and weakness within the government, among other things.

One commonly cited case of the balloon effect is that of criminal activity migrating into Central America, and particularly the Northern Triangle region (Guatemala, El Salvador and Honduras) as a result of former Mexican President Felipe Calderon's frontal assault on his country's drug cartels.

Reuter says that the balloon effect metaphor falls short in explaining this migration. While Central American nations have become more active players in the drug trade, he writes, the southward shift has been partial, and appears to have occurred more with criminal operations than drug routes. Central America is an important point of passage, but Mexico remains the principal springboard for cocaine entering the US, as well as a bastion of criminal activity, and so the shift can be seen more as an expansion and diffusion than a true migration.

Reuter does note one case in which the balloon effect appears to have occurred: in the development of West Africa as a drug route. Early in the millennium, authorities in Amsterdam, the Netherlands, began searching all passengers on flights arriving from the Netherlands Antilles after they detected heightened cocaine traffic from the island, which is located just north of Venezuela.

After an initial rise, the detection of drug "mules" dropped sharply. However, around this same time, authorities began to discover a spike in cocaine trafficked through West Africa -- with Guinea-Bissau particularly popular -- and on to Europe. As with the Netherlands Antilles route, Venezuela was identified as the exit point of the cocaine.

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Reuter's essay and the LSE report come amid an ever-growing movement advocating changes to the current drug policy paradigm, which is governed largely by the United States and its allies and has historically relied heavily on interdiction programs, crop eradication and the criminalization of consumption and possession of drugs. The call has been taken up strongly in Latin America -- shortly after the LSE report was published, a session also took place among members of the Latin American and Caribbean Community of States (CELAC) in Guatemala to discuss how the US-led model could be changed.

The balloon effect is one explanation given as to why such policies have failed to work, and have instead proved harmful and costly, particularly for producer and transit nations.

One of the most prominent examples of this effect is in regard to US-resourced coca fumigation and eradication efforts in Colombia, which helped push production back into neighboring Peru in the past decade, where fewer resources are available and aerial spraying is illegal. Peru has now become the world's top coca grower and cocaine producer.

According to Daniel Mejia of the Universidad de los Andes and Pascual Restrepo of the Massachusetts Institute of Technology (MIT), this effect also explains the shift in drug violence from Colombia to Mexico -- successful interdiction in the former country displaced the cocaine trade to Mexico. In another essay in the LSE report, they write that this phenomenon was responsible for an up to 46 percent climb in drug-related murders in Mexico after 2007.

However, as Reuter argues, the balloon effect is probably a simplification, as it is rarely interdiction efforts alone that determine criminal migration. Another, and perhaps even more apt, metaphor used to describe drug trade movements as a result of security force operations is that of the "hydra effect:" when one "head" (a capo, production zone or drug route) is cut off, two more grow back to take its place. Drug trafficking organizations are constantly morphing and evolving to maximize profit, refining trafficking techniques, reorganizing operations, gaining new recruits and shifting routes. The complexity of determining costs and gain may help explain patterns such as that described by Reuter of some drug trafficking activity moving into Central America while the primary exit point into the United States remains Mexico.

While, the direct causes of migration are difficult to identify, the reasons why drug traffickers select new destinations are not, and it is clear that weak states where there is little risk of interdiction make prime choices as both transit points and operational bases. One example is Nigeria, a country that geographically does not lie near any producer or traditional transit nations, or along any traditional cocaine routes. Yet, in addition to the country having become a transit hub, Nigerians have emerged as significant players in the drug trade, a phenomenon facilitated by severe corruption in the government in addition to factors such as their "entrepreneurial" nature, according to Reuter.

Regardless of the extent to which the balloon effect can be proved, criminal migration has major implications for drug policy as it is undoubtedly connected to the unintended negative effects that strict prohibition and interdiction policies can have. As drug trafficking migrates because of increased interdictions or changes in organizations' operations as a result of security forces actions, it often brings with it high levels of violence and the capacity to corrupt, resulting in rising insecurity and a weakening of state institutions in a growing number of countries.

This migration also highlights the limitations of current drug policy. Borders have thus far proved impossible to seal completely, and traffickers have shown to be highly adept at creating new transport routes and methods to respond to both opportunities and risks. Interdiction strategies may fill up jails with low-level criminals and drug transporters, make a dent in profits and lead to strategic changes in trafficking operations, but they have proved incapable of halting the flow of drugs.