How you aggregate two states’ democracy scores changes democratic peace results.

Evidence

The previous edition of this book provided a couple of concrete examples of how aggregation decisions can play a key role in causal and statistical analyses. One chapter, on the democratic peace, looked at aggregation options from the weakest link to the best shot, passing through the mean and the geometric mean. In this literature, most were convinced by Dixon (1994) when he argued for weakest link aggregation in order to establish the democracy value for the relationship between two states. Here the aggregation problem was combining the democracy scores of two states into a relationship variable between the two states. Dixon made a convincing theoretical argument that one should use the weakest link. The chapter in the previous edition explored how these aggregation decisions for an independent variable can and did influence the statistical results in a typical liberal peace analysis. — Gary Goertz, Social Science Concepts and Measurement, 1036

Categorization

• XREF: Hooks into the democratic peace literature the reader may know; a textbook case of methodological choices driving substantive findings.