A Blackwell-monotone information cost function assigns higher costs to Blackwell more informative experiments. This paper provides simple necessary and sufficient conditions for a cost function to be Blackwell monotone over finite experiments. The key condition involves a system of linear differential inequalities. By using this characterization, we show that when a cost function is additively separable, it is Blackwell monotone if and only if it is the sum of sublinear functions. This identifies a wide range of practical information cost functions. Finally, we apply our results to bargaining and persuasion problems with costly information, broadening and strengthening earlier findings.

翻译：布莱克韦尔单调信息成本函数为布莱克韦尔意义上更具信息性的实验分配更高的成本。本文为有限实验上成本函数的布莱克韦尔单调性提供了简洁的充要条件。关键条件涉及一个线性微分不等式系统。利用这一特征刻画，我们证明了当成本函数具有可加可分性时，其布莱克韦尔单调性当且仅当该函数为次线性函数之和。这确定了一大类实用的信息成本函数。最后，我们将研究结果应用于具有信息成本的议价与劝说问题，从而拓展并强化了先前的结论。