ICJ Biased...but toward what?

Eric A. Posner and Miguel de Figueiredo (University of Chicago Law School and University of California, Berkeley) have posted Is the International Court of Justice Biased? on SSRN. (Tip to Legal Theory Blog). The abstract:

The International Court of Justice has jurisdiction over disputes between nations, and has decided dozens of cases since it began operations in 1946. Its defenders argue that the ICJ decides cases impartially and confers legitimacy on the international legal system. Its critics argue that the members of the ICJ vote the interests of the states that appoint them. Prior empirical scholarship is ambiguous. We test the charge of bias using statistical methods. We find strong evidence that (1) judges favor the states that appoint them, and (2) judges favor states whose wealth level is close to that of the judges' own state; and weaker evidence that (3) judges favor states whose political system is similar to that of the judges' own state, and (4) (more weakly) judges favor states whose culture (language and religion) is similar to that of the judges' own state. We find weak or no evidence that judges are influenced by regional and military alignments.

Anyone note an irony here? While I confess that I have only skimmed the paper so far (and it deserves a full read), I am struck that most of these biases are truly irrelevant. While I realize that is generally considered an inherent nature of a "bias". But, what I mean by that is that while items (1) and (2), of which there appears the strongest evidence of bias are the most completely irrlevant on the list to what should be cogent international law interpretation and analysis. Honestly, I wouldn't have been surprised or disappointed to see more of what appears to be one of the weaker biases, namely, a bias toward the political system and culture of which the judge is a product. By this, I mean, that it a judge's analytical thinking would naturally (and SHOULD naturally) be influenced by having first-hand knowledge and appreciation of the internal machinations, advantages, and shortcomings of the nation-state from which they came. This knowledge should inform their decisions on legal reasoning in the supranational polity as well. It shouldn't be THE factor, but surely it should be A factor. While the statistical evidence of the paper doesn't rule this out, it appears to say that there is a weak correlation. Interesting, no?