11.1 Corporate Mergers

Corporate Mergers and Market Competition

Corporate mergers reshape industries by combining firms, which changes how many competitors exist in a market. Understanding mergers matters because they directly affect prices, product quality, and innovation for consumers.

Market Concentration

When two firms merge, the total number of competitors in that market drops. The remaining firms each hold a larger slice of the market, which reduces competitive pressure. That reduction in competition can lead to higher prices, lower-quality products, and less incentive to innovate.

There are three main types of mergers, and each affects competition differently:

• Horizontal mergers combine firms that produce similar goods or services. These directly reduce the number of competitors in an industry. For example, if two of the five major airlines merge, consumers now have fewer choices for flights.
• Vertical mergers combine firms at different stages of production (like a manufacturer merging with its supplier). These don't reduce the number of direct competitors, but they can create foreclosure, where the merged firm limits rivals' access to key inputs or distribution channels.
• Conglomerate mergers combine firms in unrelated industries. These don't directly reduce competition within a specific market, but they can increase a firm's overall market power and financial resources in ways that enable anticompetitive behavior down the line.

Antitrust Regulations

Antitrust laws exist to prevent firms from gaining so much market power that competition breaks down. Three key federal laws form the foundation:

• The Sherman Act (1890) prohibits monopolization and restraint of trade.
• The Clayton Act (1914) targets specific practices like price discrimination, exclusive dealing, and mergers that substantially lessen competition.
• The Federal Trade Commission Act (1914) created the FTC and broadly prohibits unfair methods of competition.

Two agencies enforce these laws: the Department of Justice (DOJ) and the Federal Trade Commission (FTC). When companies propose a merger, these agencies review it for potential anticompetitive effects. If a merger threatens to significantly reduce competition, regulators can block it, require the firms to sell off certain assets, or impose conditions on the deal.

The goal of antitrust enforcement is to maintain a market environment where firms compete on price, quality, and innovation rather than dominating through sheer size or anticompetitive tactics.

Market Concentration Measures

Regulators need concrete tools to assess whether a merger will harm competition. Two measures are most commonly used:

Concentration Ratios (CR4, CR8) add up the market shares of the largest firms in an industry. A CR4 sums the shares of the top 4 firms; a CR8 sums the top 8. If the four largest firms in an industry hold a combined 85% market share, the CR4 is 85. Higher ratios signal a more concentrated market. The limitation of concentration ratios is that they don't capture how market share is distributed among those top firms.

The Herfindahl-Hirschman Index (HHI) is more precise. It squares each firm's market share and sums the results across all firms in the industry:

$HHI = \sum_{i=1}^{N} s_i^2$

where $s_i$ is the market share of firm $i$ (expressed as a whole number, not a decimal) and $N$ is the total number of firms. Squaring the shares gives extra weight to firms with large market shares, which makes the HHI more sensitive to uneven distributions than a simple concentration ratio.

The HHI ranges from close to 0 (many tiny firms, near-perfect competition) to 10,000 (a single firm with 100% market share). The DOJ classifies markets using these thresholds:

• Below 1,500: Unconcentrated
• 1,500 to 2,500: Moderately concentrated
• Above 2,500: Highly concentrated

A high HHI doesn't automatically mean firms are behaving anticompetitively, but it raises a red flag. Antitrust authorities also look at the change in HHI that a proposed merger would cause. A merger that increases the HHI by more than 200 points in an already concentrated market will typically trigger a closer investigation.