For the past fifty years, the Western states have enjoyed a continuous peace among themselves. How can this be explained? According to the proponents of the `liberal peace', the Western peace rests on the pacifying effects of democratic regimes and commercial links between the states. The thesis investigates this claim theoretically and empirically, with emphasis on the `trade promotes peace' aspect of the liberal peace proposition.
To see whether there are limits to the liberal peace, this thesis investigates four core questions. Firstly, it studies the `trade promotes peace' hypothesis itself: Is the extent of the trade bonds between two states positively correlated with peace between them? Secondly, it looks at the realist counter-argument: If there is a relationship, is the impact of trade bonds really causally prior to the peace they are supposed to explain? The third question takes up an objection from `structuralist' or dependencia scholars: Can we expect any pacifying effects of highly asymmetrical trade relationships? And finally, drawing on the work of Richard Rosecrance, does the liberal peace require a certain amount of socio-economic development in the states that take part in it?
The thesis discusses the theoretical arguments in the literature and seek to model them in a game-theoretical model. A set of hypotheses from the theoretical discussion is derived, and the thesis surveys a set of large-N quantitative studies to see how these fare when confronted with historical data. Finally, some of the hypotheses are tested using Cox regression, a method that in several aspects improves on the method employed in comparable earlier studies.
The overall conclusion of the thesis is that interdependent pairs of states - dyads - really are more peaceful than non-interdependent pairs, but that this does not apply to dyads involving less-developed countries. For dyads of developed countries, on the other hand, trade is an important factor for peace. Furthermore, it is argued that the direction of causation counter-argument applies only below a certain interdependence threshold. Finally, the thesis finds no support for the idea that the `peace through interdependence' hypothesis requires a symmetrical relationship.