In a number of contexts, federal appeals court judges divide along ideological lines when deciding cases upon the merits. To date, however, researchers have failed to find evidence that circuit judges take advantage of selective publication rules to further their ideological preferences - for example, by voting more ideologically in published cases that have precedential effect than in unpublished cases that lack binding effect upon future panels. 

This article evaluates the possibility that judges engage in strategic judicial lawmaking by voting more ideologically in published cases than in unpublished cases. To test this hypothesis, all asylum cases decided by the Ninth Circuit over a ten-year period were coded for analysis, and Markov Chain-Monte Carlo methods were used to estimate the extent to which publication increased the likelihood that each judge in the data set would vote in favor of asylum. A number of Democratic appointees proved significantly more likely to vote in favor of asylum in published cases. No such pattern emerged with respect to Republican appointees. This study also confirms earlier findings that Democratic and Republican appointees divide along ideological lines to a significant extent in both published and unpublished cases. The extent of the ideological voting behavior observed in unpublished cases calls into question the validity of much research on judicial behavior, insofar as such research continues to rely exclusively upon the analysis of published opinions and ignores unpublished opinions for reasons of convenience.

David S. Law, Strategic Judicial Lawmaking: Ideology, Publication, and Asylum Law in the Ninth Circuit, 73 University of Cincinnati Law Review, 817–866 (2005).