The optimal competitive ratio for the list update problem is between 1.5 and 1.6. For lists of up to four elements, an optimal update algorithm exists. In this paper, the authors determine the lower bound for lists of at least five elements. To that end, the authors use a game tree that is composed of an irregularly structured finite list update problem (FLUP) tree with regularly structured inversion converter (IC) trees appended to its leaves. The authors find that an expected strict competitive ratio for the simplest version of FLUP is at least 1.50084, with higher lower bounds for larger FLUPs. The tree has incomplete information: the adversary who generates requests has no knowledge about the online algorithm that grants the requests.