A new working paper entitled “The Credibility Revolution in Political Science,” by Torreblanca, Dinneen, Grossman, and Xu, is making the rounds. It is an interesting, important, and thought-provoking effort to characterize how the credibility revolution has shaped the political science discipline. The authors assemble mounds of new data on journal articles in political science, and use LLMs to identify articles that employ design-based versus model-based inference. This allows the authors to characterize phenomena like the citation premium for design-based articles and other interesting features of the data.
I am interested in the implicit idea that one measures the influence of the credibility revolution in political science by counting the number of articles that employ the tools of the credibility revolution and comparing that to the number of articles that do not employ these tools. This is a reasonable answer to one specific kind of question: “are the tools of the credibility revolution being employed more frequently than other tools in quantitative political science.” The authors phrase this research question as follows:
if the credibility revolution has taken hold, design-based methods should increasingly displace purely model-based approaches in quantitative explanatory research, with growth spread across multiple design-based strategies
Again, this is a useful hypothesis and we should know the answer to it (spoiler alert: the answer is yes). But this way of thinking underestimates the impact of the credibility revolution on political science. Specifically, one of the other implications of the credibility revolution is that one should deliberately not use causal language or employ design-based inference when one’s quantitative research does not seek to estimate a causal effect, or when no design-based logic of inference is credible.
I count myself as a partisan in the credibility revolution, but this means something different to me than it might to some of my other fellow partisans. To be a partisan does not imply that one only employs design-based inference; rather, it means always paying close attention to the distinction between causal and non-causal claims and the requirements for inferring causality from an observed association between two or more variables. Here (PDF) is an example from my own research:
In this article I reinterpret Ng, Rangel, Vaithilingam, and Pillay’s analysis in this issue of pro-BN voting in Peninsular Malaysia in Malaysia’s 2013 general election. I show that the authors’ statistical methods are inappropriate for testing whether district ethnicity predicts district-level BN vote share, and that their modeling choices result in tests of hypotheses that do not exist and cannot be derived from standard theoretical approaches to ethnic voting in Malaysia. I then provide a range of statistical evidence that supports three main conclusions: (1) ethnicity and district area (a proxy for urbanization) both predict BN vote shares at the district level, (2) neither the effect of ethnicity nor of district area can be reduced to the other, and (3) there is no interactive effect between ethnicity and urbanization. These results are in direct contradiction with the authors’ results, and apply equally in Peninsular Malaysia and the entire country. I also discuss the broader issues that emerge when testing competing theories of BN vote share.
This article does not purport to estimate a causal effect, and goes on at some length about the conceptual and empirical challenges of prediction from two highly correlated explanatory variables. You could not argue that this is an example of design-based inference in action, and yet this is a case where the credibility revolution caused* an author to not use causal language or design-based inference in quantitative explanatory research. I think the inferences are more compelling because of it.
One of the upshots of the credibility revolution might be better non-causal empirical research, not just more and better causal research designs.
NOTE
* Counterfactually, no way I would have written this piece this way had I not been exposed to the logic of design-based inference from early in graduate school.

