Is the United States destined to decline in the twenty-first century? This is a seemingly simple question, but one that International Relations theorists seem destined to debate without resolution. How should we measure power? What are the most relevant economic and military indicators of national power? How should we weigh the various components of national power in order to reach an overall assessment of the future balance of power in the international system? Are structural and material indicators reversible or irreversible? Can specific policy decisions, ideas, and strategies substantially reverse or accelerate national decline?