Rivalrous advertising spending between two megacorps everyone already knows is zero-sum. You’re spending money just because the other guy increased spending, an

Rivalrous advertising spending between two megacorps everyone already knows is zero-sum. You’re spending money just because the other guy increased spending, and market share stays the same. But you can’t not spend or you might lose market share. Now you’re both spending more to achieve the same result. [edit] zero sum in terms of the market-share game—the size of the pie stays the same, you’re just adjusting who gets how much. Negative sum for the overall game in the case that total spending increases.