According toRon Suskind's book The One Percent Doctrine, in the days following the terrorist attacks of Sept. 11, 2001, the Bush administration in essence adopted a "take no chances" policy on national security: that is, the government would treat a terrorist threat with even a 1-percent chance of occurring as if it were a certainty.

Suskind argues that philosophy has driven most of government security activities in the days since.

Add that to the widespread concern that terrorists might see international shipping containers as a perfect way to smuggle something like a dirty bomb into the country, and it's surprising, in a way, that government has not pushed harder for 100-percent inspection of containers. It certainly has been suggested. But fortunately, rational voices have persuaded Congress that imposing any such rule would bring gridlock to international commerce. Instead, the Department of Homeland Security and other agencies, along with business, have developed what they call a layered approach to container security. Programs like the Container Security Initiative and the Customs-Trade Partnership Against Terrorism are designed to help weed out shipments that might present a risk.

In the meantime, technological approaches to identifying risky cargoes have been undergoing testing. The best known example is in Hong Kong, where all containers entering port gateways undergo radiation and gamma ray scanning. Congress this fall mandates, among other things, container screening projects at overseas ports to test 100-percent screening. Other technology on the market combines radiation detection and active tags that could be deployed at a relatively low cost per container. (See our report on container security beginning on page 38.)

Given the millions of containers that flow in international commerce and the varying financial abilities, not to say willingness, of foreign ports or shippers to invest in any technology that doesn't offer business benefits, the issue won't be an easy one to resolve. Obviously, the government could impose 100-percent screening at U.S. ports. But in the case of something like a dirty bomb, discovery of a threat when it has arrived on our shores is too little, too late.

Clearly,the threat is real, though its extent is difficult to gauge. The financial cost of any effort is also real, and who should bear the burden is the subject of much debate. What is 100-percent clear: Shippers are right in the middle, like it or not.