Excess fishing capacity and the growth in global demand for fishery products have made overfishing ubiquitous in the world's oceans. Here we describe the potential catch losses due to unsustainable fishing in all countries' exclusive economic zones (EEZs) and on the high seas over 1950-2004. To do so, we relied upon catch and price statistics from the Sea Around Us Project as well as an empirical relationship we derived from species stock assessments by the U. S. National Oceanic and Atmospheric Administration. In 2000 alone, estimated global catch losses amounted to 7-36% of the actual tonnage landed that year, resulting in a landed value loss of between $6.4 and 36 billion (in 2004 constant US$). From 1950-2004, 36-53% of commercial species in 55-66% of EEZs may have been overfished. Referring to a species-level database of intrinsic vulnerability (V) based on life-history traits, it appears that susceptible species were depleted quickly and serially, with the average V of potential catch losses declining at a similar rate to that of actual landings. The three continental regions to incur greatest losses by mass were Europe, North America, and Asia-forming a geographic progression in time. But low-income and small island nations, heavily dependent on marine resources for protein, were impacted most profoundly. Our analysis shows that without the inexorable march of overfishing, ~20 million people worldwide could have averted undernourishment in 2000. For the same year, total catch in the waters of low-income food deficit nations might have been up to 17% greater than the tonnage actually landed there. The situation may be worst for Africa, which in our analysis registered losses of about 9-49% of its actual catches by mass in year 2000, thus seriously threatening progress towards the UN Millennium Development Goals.