The paper explores the relationship between risks and market organisation by means of two case studies. After defining the two concepts, it analyses how risks influence the functioning of markets, by means of the theory elaborated by Knight (1921). The Knightian focus on the role of judgments in risks analysis implies that the concept of rationality has to be enlarged beyond the rational choice theory. Similarly, markets cannot be defined anymore as simply an equilibrium between supply and demand: they are a special type of institution. Therefore, the analysis centres on how people make decisions and apprehend risks in relation to market structures. In the rest of the paper, two of the most prominent food safety crises in recent years are analysed based on this conceptual framework: the milk powder crisis in China (2008) and the sanitary crisis following the Fukushima nuclear accident (2011). It is shown that they represent two types of market risks, one generated by the food market organisation and the other one related to the definition of the product quality.

本文通過兩個案例研究探討風險和市場組織之間的關系。文章界定這兩個概念後，根據奈特（1921）闡述的理論分析風險如何影響市場運作。奈特主義者注重風險分析中決定的作用，意味著理性概念需要被擴大至理性選擇理論以外。同樣，市場不能再被定義為簡單的供應和需求之間的平衡：他們是一種特殊類型的體制。因此，文章的分析聚焦於人們如何作出決定，和理解風險與市場結構的關系。文章其余的部分基於這個概念框架，分析近年兩個最突出的食品安全危機：中國的奶粉危機（2008年）和福島核事故後的衛生危機（2011年）。它們代表兩種類型的市場風險，一種源自食品市場的組織，另一種關乎產品質量的定義。

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