SHOCKING NEWS: No ship with an armed security team aboard has been successfully pirated.

In 2011, the U.K., Greece, Norway and other major maritime nations began letting their merchant ships carry armed private-security personnel for self-defense in hazardous waters. This overcame longstanding legal and cultural barriers such as stringent local firearms laws and fears of liability.

The result? Successful hijackings off Somalia fell by half to 14 in 2012 from 28 in 2011, and overall attacks dropped to 75 from 237. Through the third quarter of 2013, there have been just 10 incidents, with two hijackings.

The main reason for this drop is that Somali piracy is an industry like any other, albeit far more brutal. When risks are low and profit margins are high, piracy flourishes. Investors on land buy shares in a piracy venture, funding weapons and equipment in exchange for a stake in any ransom. Thus to suppress piracy, the return on investment must be made unfavorable.

A major step toward making piracy less attractive to investors has been merchant vessels’ increased adherence to the industry’s Best Management Practices, which advise ships to travel at over 18 knots, fortify access points and take evasive action when attacked. Yet many vessels, such as bulk carriers and large tankers, are too “low and slow” to fully comply with these practices and need additional protection.

Armed private security fills the breach not by winning high-octane gunfights against pirates—although there have been a few—but through deterrence. Security companies know that most pirates are profit-seeking criminals, not fanatical terrorists. Armed guards, either on merchant ships or in their own escort boats, make their presence known, firing warning shots if pirates approach. This almost always persuades hijackers to abort their mission and seek out easier prey.

The firepower necessary to achieve this deterrence has proven cheap enough that private security has been widely adopted by the shipping industry.

Yes, just as homeowners with guns make home invasions less likely. Given that merchant vessels have been armed for nearly all of human history, the real surprise is that anyone finds this surprising. On the other hand, the near-elimination of piracy was a major accomplishment of the two centuries of British/American naval dominance that appears to be coming to an end. This is just one small way in which the world will pay a price.