Advertising messages vie for scarce attention. “Junk” mail, “spam” e-mail, and telemarketing calls need both parties to exert effort to generate transactions. Message recipients supply attention depending on average message benefit, while senders are motivated by profits. Costlier...

Advertising competes for scarce consumer attention, so more profitable advertisers send more messages to break through the others' clutter. Multiple equilibria can arise: more messages in aggregate induce more "shouting to be heard", dissipating profit. Equilibria can involve a small range of...