Market share objectives are prominent in many industries, especially where managers pay much attention to league table rankings. This paper explores the strategic rationale for giving managers incentives based on market share, motivated by evidence from executive compensation practice in the automotive and investment banking industries. Strategic incentives for market share dominate the well-known sales revenue contracts analyzed in much of the literature, but perhaps surprisingly also lead to less competitive outcomes. The more general lesson is that, when competing in strategic substitutes, players will wish to commit to aggressive conduct, but also make their behaviour less manipulable by rivals.