Do longer briefs correlate to success for Appellants?

I cannot think of a single writing seminar I have attended or book I have read that did not emphasize succinctness. Now comes a paper published at the Social Science Research Network, “Too Many Notes”? An Empirical Study of Advocacy in Federal Appeals (download link),which, if this excerpt from the abstract is any indication, appears to raise a statistical challenge to that line of thinking, at least in the Ninth Circuit:

Given the central role of written briefs in the process, we should examine seriously the frequent complaint by appellate judges that briefs are too long and that prolixity weakens persuasive power. In a study of civil appeals in the United States Court of Appeals for the Ninth Circuit, we discover that, for appellants, briefs of greater length are strongly correlated with success on appeal. For the party challenging an adverse decision below, persuasive completeness may be more important than condensed succinctness. The underlying cause of both greater appellant success and accompanying longer briefs may lie in the typically complex nature of the reversible civil appeal. In light of our findings, the current proposal to reduce the limits on number of words in federal appellate briefs may cut more sharply against appellants.

Every opening brief presents a struggle between “persuasive completeness” and a “condensed succinctness.” The ideal opening brief, of course, is complete and succinct. Sometimes, that can be accomplished, but not always (just ask Jeff Skillings’s lawyers), and maybe not even often, especially if one measures succinctness in absolute terms. But aside from rule-imposed limits, I think the the length of a brief has to be judged relative to its completeness — the number of issues raised and how complex the issues are. A brief of 7,000 words may be quite verbose if it raises only one or two simple issues, while a brief of 14,000 words may be a concise presentation of far more numerous and complex issues.

Update: the article has triggered this discussion thread at LinkedIn.