我們利用Bewley (1986) 對於Knight 不確定性的詮釋，重新檢視Rothschild & Stiglitz (1976) 的競爭性保險市場模型。在資訊對稱時，保險市場上會有多重均衡，且均衡契約種類與稟賦、出險機率以及意外損害的程度有關，而不是如預期效用理論分析的保險行為所得出消費者必定會選擇全險的結論。在具資訊不對稱時，即保險公司無法區分被保人的出險機率，我們得到如同Rothschild & Stiglitz 混合均衡必不存在的結論；而分離均衡，在某些狀況之下，保險業者可能對低風險消費者提供全險或者是超額險，而並非Rothschild & Stiglitz (1976) 所提之低風險消費者會因為高風險消費者的存在而僅能承保部分險。

We use Bewley’s (1986) notion of Knightian uncertainty to reexamine competitive insurance market analysis of Rothschild and Stiglitz (1976). In the symmetric information case, there may be multiple equilibria, and the equilibrium insurance contracts depend on endowment, probability of accident and loss of an accident, which is in contrast to the result that consumers would always choose full insurance contract in a competitive insurance market as predicted by the analysis relying on expected utility theory. When insurance companies cannot observe insuree’s probability of accident, we find that a pooling equilibrium would not exist, separating equilibrium would exist under some circumstances, and, different from the Rothschild and Stiglitz’s (1976) result, the insurance company may offer full- or over-insurance contract to low risk consumers.

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