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Northwestern University Law Review

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The modern trend is for investors to diversify. Shareholders who own one S&P 500 firm tend to own many of the others as well. This trend casts doubt on the traditional compensation and deterrence rationales for legal rules that hold corporations liable for the acts of their agents. Today, when A Corp sues B Corp (for breach of contract, theft of trade secrets, or any other legal wrong), many of the same shareholders own both the plaintiff and the defendant. For these shareholders, damages just shift money from one pocket to another, minus of course lawyer fees. We offer here a new rationale for corporate liability in such cases of “intraportfolio litigation.” Although corporae managers are typically rewarded for maximizing firm profits, what shareholders really care about is overall portfolio value. Firm-on-firm lawsuits can reduce principal-agent conflict by assigning intraportfolio costs to the managers responsible for them. Firm-specific financial data thus become a better tool for diversified shareholders to use in motivating and evaluating managers. Not all intraportfolio litigation can be justified on informational grounds, however. For example, securities fraud class actions against corporations lack informational value because the damages awards overstate the intraportfolio harm. Our theory thus provides lawmakers with a framework for distinguishing between value-creating and value-destroying lawsuits among diversified shareholders.

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