Panamanians have overwhelmingly approved a ,25-billion plan to widen their transcontinental canal, a project that will allow the world’s biggest ships to sail between the Pacific and Atlantic oceans. About 80% of the gross domestic product of Panama, with a population of three million, is linked directly or indirectly to canal activity.

Voters headed to the polls on Sunday for a referendum on a ,25-billion plan to widen the Panama Canal, a strategic waterway whose main users are the United States, China and Japan. Proponents say the canal, through which roughly 4% of world trade flows, badly needs an overhaul to remain competitive against other maritime routes.