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To evaluate the practical effects of presidential vs. parliamentary rule, Gerring, et al. (2008) use a complex global data set. The hypothesis of the research is that the type of executive governance used does have concrete and measurable effects on policy and policy outcomes. The researchers use 14 indicators to measure the dependent variables including those within the categories of political development, economic development, and human development. An analysis of the data reveals favoritism for parliamentary systems because of their association with general "good governance," (Gerring, et al., 2008, p. 328). The authors conclude that parliamentary systems are "a more reliable vehicle for good public policy," (p. 353).

The study has several methodological weaknesses that prevent it from being an authoritative source of data on the subject. Most of the findings reveal correlative, rather than causal, connections between the dependent variables and the type of executive structure in government. Moreover, the potential of intervening and extraneous variables has an adverse effect on internal and external validity. The authors go to great lengths, however, explaining each data set and set of correlative relationships. Assumptions are rooted in prior research or theory. A few more examples of exceptions to rules, and explanations of those exceptions would help bolster the overall impact of the Gerring et al. (2008) study.

Still, the research is ambitious and as thorough as possible under the circumstances. The dependent variables are meaningful, especially because the authors state the purpose and application of their research as being how to properly consult budding democracies on their constitutional development. Called "constitutional engineering," the process of determining whether a presidential or a parliamentary system is a critical issue. It would best benefit the budding nation to access hard, empirical evidence that points to the issues that are most pressing: whether those issues be humanitarian/social; economic; or political. Although the authors come to a definitive conclusion that parliamentary systems offer a superior means of creating good, flexible governance, the question of local or regional diversity remains salient.