We study the monotonicity of information costs: more informative experiments must be more costly. As criteria for informativeness, we consider the standard information orders introduced by Blackwell (1951, 1953) and Lehmann (1988). We provide simple necessary and sufficient conditions for a cost function to be monotone with respect to each order, grounded in their garbling characterizations. Finally, we examine several well-known cost functions from the literature through the lens of these conditions.

翻译：我们研究信息成本的单调性：更具信息量的实验必然成本更高。作为信息量的评判标准，我们采用Blackwell（1951, 1953）和Lehman（1988）提出的标准信息序。基于这些信息序的随机化表征，我们为成本函数相对于每种信息序的单调性提供了简洁的充要条件。最后，我们通过这些条件来审视文献中若干经典的成本函数。