Risky Markets explores a crucial moment in the history of insurance, when tools designed to tackle sea risks were in their first making. Renaissance Florence is the setting for one of the first attempts to develop a market specialized in protecting maritime trade. Drawing on a unique collection of sources, the book provides a wide ranging account about the players, institutions, business practices and organizations of the insurance business, shedding light on the forecasting techniques underwriters used. Ceccarelli shows that the market was a small club where trust relations and shared codes of conduct prevail over competition. In a world without probability this was the way by which a business community managed transforming uncertainty into a calculable risk.