We analyze the impact of passive partial ownership (PPO) on horizontal mergers. We show that antitrust authorities ignoring the effects of previous PPO acquisitions invite sneaky takeovers: a PPO is strategically used prior to a full takeover to get a merger approved which is in fact detrimental...

We analyze horizontal mergers when the acquirer holds a passive partial ownership stake (PPO) in the target firm prior to the merger. We show that a PPO reduces the minimal synergy level necessary to make a merger beneficial for consumers. It follows that an antitrust authority ignoring existing...