This refers to a business strategy where a company expands its control over its industry by acquiring similar firms at the same level of the supply chain. A classic example would be a major oil refinery purchasing other oil refineries, thereby consolidating its market share and reducing competition within that particular sector. This differs from vertical expansion, which involves controlling different stages of production or distribution.
The implementation of this strategy during the late 19th century allowed industrialists to create monopolies and exert significant influence over prices and market conditions. This consolidation of power often led to debates about the ethics of big business, government regulation, and the balance between economic growth and fair competition. It shaped the economic landscape and fueled progressive era reforms aimed at curbing monopolistic practices.