United States v. Philadelphia National Bank
Citation: 374 U.S. 321 (Supreme Court, 1963)
Facts
Philadelphia National Bank (PNB) proposed to merge with Girard Trust Corn Exchange Bank, which would create the largest bank in the Philadelphia metropolitan area and the second largest in Pennsylvania. The merged bank would control over 30% of the relevant market for commercial banking services in the four-county Philadelphia area. The government sued to block the merger under § 7 of the Clayton Act.
Issue
Whether a bank merger that would result in the combined entity controlling 30% of a local banking market, with a combined market share of the top two firms exceeding 59%, violates § 7 of the Clayton Act.
Holding
Yes. The Supreme Court held the merger violated § 7 and established a presumption of illegality for mergers that produce high market concentration or significantly increase concentration in already-concentrated markets.
Rule
A merger that produces a firm with an undue percentage share of the relevant market and results in a significant increase in concentration of firms in that market is inherently likely to lessen competition substantially and is therefore presumptively unlawful under § 7. This structural presumption shifts the burden to the merging parties to rebut illegality. The presumption may be rebutted by evidence that the market share statistics give an inaccurate picture of competitive effects.
Significance
Philadelphia National Bank is the foundational case for structural analysis in horizontal merger review and remains the source of the “structural presumption” that underlies the DOJ/FTC Merger Guidelines. The case established that courts should look primarily at market concentration data (formalized into HHI thresholds in the Guidelines) and presume harm from large concentration increases, placing the burden on defendants to demonstrate why the structural evidence is misleading. It is the starting point for every merger analysis in antitrust law.