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 *Arguments excluded "There are also some difficulties in the application of statistical methods to the problem, especially to question of causation." Many studies and arguments mentioned here excluded: "Supporters of the DPT do not deny that other factors affect the risk of war but argue that many studies have controlled for such factors and that the DPT is still validated. Examples of factors controlled for are contiguity, power status, alliance ties, militarization, economic wealth and economic growth, power ratio, and political stability. Studies have also controlled for reverse causality from peace or war to democracy."