No changes can be more far-reaching in their social effects than those in economic structure. The economy provides the work context in which most men spend most of their active hours; it supplies the resources upon which their standard of living is based; and it moulds many of their relationships within their own families and in the wider social structure. But as a conscious instrument of change, while undoubtedly critical, the economy is uncertain. We shall see that there are times, such as during the First World War, when direct economic changes are brought about through the deliberate intentions of government. But it is much more common, whatever political intentions may be, for these changes to occur in a more mysterious fashion. The late nineteenth and early twentieth century is generally recognized as an important turningpoint in British economic history, when the British dominance of the world economy won in the early nineteenth century began to be steadily eroded. Why this should have been so is much more open to debate.