ON THE REPRESENTATION OF THE NESTED LOGIT MODEL
用两行证明解决了Ben-Akiva 1973年博士论文中关于嵌套Logit模型随机效用表示的长期猜想，并给出了Gumbel copula耦合下两个Fréchet随机变量相关性的闭式公式。
In this paper, we give a two-line proof of a long-standing conjecture of Ben-Akiva in his 1973 PhD thesis regarding the random utility representation of the nested logit model, thus providing a renewed and straightforward textbook treatment of that model. As an application, we provide a closed-form formula for the correlation between two Fréchet random variables coupled by a Gumbel copula.