There were so many changes in economic structure and relationships during the first half of the twentieth century, so many vicissitudes of fortune both for national communities and for social groups within them, that long before the outbreak of the second world war in 1939 it was clear that there could be no return to the theory and practice of international economic interdependence as both were understood in the world before the outbreak of the first world war in 1914. Although subsequent changes since 1939—and more particularly since 1950—have in some respects been even more drastic, there was such a sharp contrast in experience between the world before 1914 and the world after 1914 that contemporaries found it difficult to adapt themselves to new circumstances or to meet the challenge of new problems.

Before 1914, important economic changes, like the growth of the industrial power of the United States or the development of new technologies based on steel and electricity, took place within a system of specialisation which did not change as a whole: mutability in particulars seemed to be consistent with general stability. After 1918, serious maladjustments hi the internal economies of the European countries, along with boom and slump of unprecedented dimensions in the United States, involved such dislocations and shocks to the international economy that there was a tendency to idealise the state of affairs before the debacle. At the same time critics were emerging who pointed to serious limitations and shortcomings.