By using a unique data set from the Turkish cement industry, we analyze the impact of privatization on the market value of rival firms. Privatization increases efficiency, which is bad news for rivals. But if an incumbent buys a state owned firm, this leads to a higher market concentration which is good news for rivals. We show that privatization leads to overall positive abnormal returns for rivals because the concentration effect outweighs the efficiency effect. Consistent with our theory, this effect is reinforced when the initial market concentration is high.