This article shows how asymmetric information shaped slavery by determining the likelihood of manumission. A theoretical model explains the need to offer positive incentives to slaves working in occupations characterized by a high degree of asymmetric information. As a result, masters freed (and, more generally, rewarded) slaves who performed well. The model's implications are then tested against the available evidence: both in Rome and in the Atlantic world, slaves with high asymmetric information tasks had greater chances of manumission. The analysis also sheds light on the master's choices of carrots versus sticks and of labor versus slavery.“Whatever work he does beyond what is sufficient to purchase his own maintenance can be squeezed out of him by violence only.”Adam Smith,The Wealth of Nations1“[N]or because they are slaves do they less than free men need the lure of hope and happy expectation.”Xenophon,The Economist2