"To ensure unrestricted sea lines of communication (SLOCs) in Southeast Asia (SEA), the U.S. Navy is assigned the task of helping to maintain clear maritime passage through the sea lanes of the region. For many years, the prime concern was military, not economic, as the United States required secure maritime transport via SLOCs in case of war. Now the emphasis has shifted to the economic component of our national security, a policy reaffirmed when the United States announced it would not accept disruption of trade in the South China Sea. In March and again in May, 1995, Secretary of State Christopher warned quarreling claimants to the Spratly reefs not to interfere with international shipping. What is the economic logic behind the American stance on freedom of navigation for commercial shipping? For the U.S. a concern is: 'Who benefits from keeping sea lanes open, and how much do they benefit?' A related question is: 'Who would be hurt if the sea lanes were closed, and how much would it hurt them?'"
Defense Technical Information Center (DTIC): http://www.dtic.mil/dtic/