Is the Democratic Peace Correlation Spurious?

The Spuriousness Critiques

The first set of critiques is that the observed correlation between dyadic democracy and peace is spurious. More informally, the critique is that the observed peace between democracies is caused by factors other than democracy, and not by democracy itself. More rigorously, consonant with the definition of a law provided above, the observed peace between democracies would not support the counterfactual that taking a pair of democracies and rendering one of them non-democratic would make their relationship less peaceful. Whether the democratic peace is spurious or causal is not merely a semantic quibble. Scientists across the social and natural sciences maintain a deep interest in determining whether an observed correlation is causal or merely spurious. Identifying causation is critically important in translating scientific findings into policy recommendations, in areas such as dietary guidelines, poverty reduction, education, fighting disease, and others.

Scholarship making the claim that the democratic peace is spurious frequently takes the following form. On the theoretical side, an alternative explanation for the causes of peace is provided. On the empirical side, a critique will present a previously published multivariate regression analysis showing support for the dyadic democratic peace, and then show that adding to this regression analysis an additional independent variable that measures the new, alternative explanation will cause the dyadic democratic peace variable to become statistically insignificant. Adding the new variable is justified from a methodological point of view as a means of improving the model by reducing what is referred to as “omitted variable bias.” The critique then draws the inference that because the inclusion of this additional variable (or variables) renders the democracy variable statistically insignificant, the initial result was flawed because of omitted variable bias. In turn, the inference is that the initial observed correlation between democracy and peace is spurious rather than causal, and that as a causal hypothesis the democratic peace proposition is not supported. A further implication is that because the democracy-peace relationship is spurious rather than causal, policy-makers should avoid concluding that spreading democracy will in turn cause the world to be more peaceful.5

Scholars have made a number of arguments about the spuriousness of the democratic peace, that is, they have pointed to a series of different variables that if included in multivariate regressions render the democracy-peace correlation statistically insignificant. The oldest and perhaps most central proposition of this type is the realist argument that common national interests rather than joint democracy explain peace. As indicated above, realism proposes that international relations are fundamentally driven by national interests, and not by domestic politics or institutions. Further, realism places no faith in the ability of public opinion coupled with democratic institutions to be a force for peace, because public opinion is not necessarily rational or peaceful; and because elected and other leaders can circumvent the constraints of public opinion through secrecy and other forms of manipulation (e.g., Mearsheimer, 2011; Rosato, 2003; Schuessler, 2015). Historically, the collapse of the international order in the interwar period made realist critics such as E. H. Carr, Walter Lippmann, and Hans Morgenthau deeply skeptical of Wilson’s vision that the spread of democracy could support global peace. Waltz (1959; 1993, p. 78) from the 1950s through the 1990s was also critical of the Kantian hope that democracy would bolster peace, proposing that the brutally competitive nature of the anarchic international system forces different types of political regimes to adopt converging foreign policies in order to survive. Realists in turn proposed that any observed correlation between democracy and peace must be spurious, and in turn that the observed peace between democracies was caused by commonalities in interest and/or by a functioning balance of power rather than by regime type (see Layne, 1994; Mearsheimer, 2014; Rosato, 2003).

Several quantitative studies have endeavored to demonstrate that decisions for war and peace are caused by realist factors such as national interests and the balance of power, and not by regime type. In the 1990s, realist critics took note that the first wave of rigorous quantitative democratic peace studies focused on the 1950–1985 time period, suggesting that especially during this Cold War period democracies were unwilling to fight each other not because of institutions or norms, but because North American, East Asian, West European, and South Pacific democracies needed to balance together against a common Communist threat. A variant of this argument is that peace among democracies during the Cold War was maintained by American hegemony, that a democratic America managed conflict among states within the democratic, anti-Communist bloc to solidify its global power position.

These studies took different approaches to demonstrating this point. Gowa (1999) argued that the democratic peace was a temporal phenomenon; that pairs of democracies were indeed less likely to become involved in militarized interstate disputes or wars after 1945; were less likely than other pairs of states to become involved in MIDs but not wars from 1919–1938; and were as likely to become involved in wars and MIDs before World War I. That is, she measured the presence of common interest indirectly by comparing political eras, arguing that democracies shared common interests after 1945, confronting the Communist threat, and therefore unsurprisingly were less likely to fight each other. Before World War II, she argued, when there were fewer common interests among democracies, the observed correlation between democracy and peace disappears.

Gartzke (1998) took a more direct approach toward testing the same theoretical supposition. He also proposed that common interest rather than joint democracy was the true cause of the observed peace between democracies, especially in the post-1945 period. Rather than comparing eras as Gowa did, he analyzed the post-1945 period, but included in his regression analysis a variable of common interest, measuring how similar were the United Nations General Assembly voting patterns of two states. He found that this variable was statistically significantly related to dyadic peace, and that inclusion of this variable rendered the joint democracy variable statistically insignificant as an explanation of dyadic peace. Some observers have also suggested that the observed peace between democracies is caused by geographic factors rather than regime type (Worley, 2012).

An additional cut on the national interests argument is that conflicts are caused by interstate disputes over contested issues, like territory, and not by regime type. Gibler (2012) focused on territorial disagreements between states. He proposed that territorial disagreements are the fundamental cause of conflict between states, and that inclusion of variables that measure the stability of borders, and therefore the absence of territorial disagreement, rendered the joint democracy independent variable to be statistically insignificant as a cause of peace.

A second cluster of spuriousness critiques focuses on economic rather than political factors. A perhaps more limited version of this critique is that there is a peace among democracies, but only in the developed world and not in developing areas such as sub-Saharan Africa (Henderson, 2008). A more ambitious form of this critique is that development and markets are the true causes of peace, and that democracy is uncorrelated with peace when these factors are accounted for. There are some variants of this observation. Gartzke (2007) focused on higher levels of economic development, proposing that more developed states enjoy lower marginal gain from winning a war over economic assets, and in turn are less likely to become embroiled in war. Conceptually, there is a related strand of research that war has become obsolete as states’ economies have become more advanced and rely more on trade and the global market (Rosecrance, 1986). This point is also related to the more popular assessments of a “McDonald’s Peace,” the observation that countries with McDonald’s restaurants have never fought, McDonald’s being a sign of development (Friedman, 2000, ch. 21), or the “greens peace,” the observation that nations in which golf is sufficiently popular (again, a sign of development) never fight each other (Plotz, 2000). Mousseau (forthcoming; 2009) made a different argument, proposing that only some forms of economic development nurture peace. He proposed that market-based societies place a cultural emphasis on contracts and the law. In turn, this cultural emphasis on law percolates into foreign policy preferences, pushing such states to prefer nonviolent means of conflict resolution. Mousseau proposed that inclusion of a variable measuring this emphasis on contracts and law, what he termed to be “contractualism,” renders the joint democracy variable statistically insignificant.

A third critique focuses on gender. One of the central questions asked in the study of gender and politics is the relationship between gender and war, with many arguing that biological sex and/or cultural constructions of gender are critical factors affecting the onset of political violence. Further, some scholars have used gendered perspectives to critique the proposition that democracy causes peace. Allison (2001) used Kant’s framework of perpetual peace to propose that the key cause of international peace is a feminine perspective on interpersonal care rather than joint democracy. Wisotzki (2015) suggested that gender equality encourages both democracy and peace, though she stopped short of proposing that there was no causal relationship between democracy and peace. Hudson and colleagues (2012) used new data on the physical security of women and political violence, finding that lower physical security of women makes political violence more likely, and that the inclusion of gender equality in the analysis renders democracy an insignificant determinant of peace. Notably, Hudson and colleagues’ unit of analysis is the state rather than a pair of states, and their measure of violence incorporates many types of violence, including intrastate violence. One of Hudson’s coauthors in earlier studies of the causes of interstate violence found in multivariate analyses mixed evidence that both measures of gender inequality and democracy were statistically significant causes of peace (Caprioli, 2000; Caprioli & Boyer, 2001).

Another possible critique, not quite leveled explicitly by any critics, is that common culture and common identity, rather than democracy, cause peace. This is perhaps an implication of Huntington’s (1996) “Clash of Civilizations” thesis: that differences in civilization or culture rather than regime type determine conflict between states.