Leadership long-cycle analyses emphasize the global political economy, sea power, and the cyclical rise and fall of maritime powers. Ludwig Dehio's interpretation of European international politics stressed regional politics, land power, and the cyclical rise and fall of continental powers. Since neither framework totally ignores what the other accentuates, a merger of the two perspectives is quite feasible and results in improved explanatory power. As an illustration, several of Dehio's generalizations about the nature and timing of regional power concentration are tested for the period 1494–1945. The outcome suggests that peaks of regional and global power concentration alternate. Global reconcentration is stimulated, at least in part, by the threat posed by a rising regional challenger.
There is a distinctively repetitive quality about trade policy problems. Domestic economic growth slows; producers seek protection against foreign competitors; and national decision makers raise barriers to trade while at the same time criticizing their counterparts in other governments for engaging in similar practices. Because trade is one of the more important topics in international and comparative political economy and because this scenario has played itself out more than a few times, it is not surprising that a number of theorists have sought to model the underlying processes thought to produce movements toward and away from protectionism.