Identifying Monopoly Market Structure

Consider an industry where a single firm has complete control over the entire market supply of a product, leading to significant pricing power. Additionally, this firm experiences economies of scale, resulting in a downward-sloping long-run average cost curve. In this context, the firm has the ability to set prices above the marginal cost and potentially earn positive economic profits in the long run.

Based on this scenario, which market structure does this industry exemplify?