Can horizontal mergers transform an industry from oligopoly to monopolistic?

Yes, horizontal mergers can potentially transform an industry from an oligopoly to a monopolistic structure by significantly reducing the number of competitors in the market. When firms in the same industry combine, they may gain increased market share and pricing power, leading to less competition. This can result in higher prices and reduced consumer choices, as the merged entity may dominate the market. However, regulatory scrutiny often aims to prevent such outcomes to maintain competitive markets.