More recent work, starting with that of John "Jack" Gallagher and Ronald Robinson in the 1950s, has questioned the traditional definition, positing instead that the two were mutually constitutive and maintaining that, despite the apparent temporal inconsistencies inherent in their separate existences, each formed simultaneously in relation to the other. Gallagher and Robinson were socialists, observing the rise of the economic power of the United States in the developing world at a time when the African colonies of the British Empire were being granted independence; both scholars held that British and American expansion of overseas influence were ultimately developed along similar lines.