Based on generalized run-off triangle, we introduce multiplicative model and its marginal-sum estimation in chapter 2. We get that the marginal-sum estimation is the chain ladder estimation.

基于一般的流量三角形，我们在第二章中提出了乘法模型及边际和估计，并证明了在该模型下，参数的边际和估计就是链梯法估计。

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This is usually said to be, a rule of thumb, about 20% of the sum collected or, in another formulation, perhaps 35% of the marginal revenue of the system.

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