market share liability

Market share liability is a legal responsibility and tort theory where all manufacturers are liable for an injury caused by a defective product based on their share of the market when the harm occurred. Under market share liability, the plaintiff of an injury case can recover even if they do not know the direct manufacturer of the product that caused the injury. Therefore, the burden of proof shifts from the plaintiff to prove which manufacturer is liable, to the manufactures to prove they are not liable. However, this doctrine is not widely accepted, only a handful of states recognize market share liability in their courts.

In order to establish market share liability, the plaintiff must prove five factors:

  1. The manufacturer defendants manufactured an interchangeable product that caused the plaintiff’s personal injury;
  2. The product contained a design defect that caused the harm;
  3. Each manufacturer defendant sold the interchangeable product in an unreasonably dangerous manner;
  4. The plaintiff is unable identify the specific manufacturer of the product that caused their injury; and
  5. The number of manufacturers joined as defendants in the suit account for a substantial share of the market.

Market share liability is often found in products liability cases where the direct cause of the harm cannot be pinpointed to a certain point in the manufacturing to selling process. For example, in Conley v Boyle Drug Co., the Florida Supreme Court held that the manufacturer defendants of the DES drug were liable for the plaintiff’s cancer that was caused by the drug, unless the defendants could prove they did not manufacture the drug at the time of the plaintiff’s injury.

[Last reviewed in August of 2024 by the Wex Definitions Team]

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