The present invention relates to the assignment of calls to groups of call handlers in a call center environment. According to certain aspects, the present invention achieves an optimal balance between the level of service and overall cost by assigning a “common” pool skill to all call handlers in the system and by secondarily assigning one or more additional “rare” pool skills to each call handler. In this configuration, any call handler may receive calls (or other multiple media work assignments) from the states in the common pool while also receiving calls from the states in their additional rare pool(s). According to other aspects, a method according to the invention optimizes the selection of the skills to be included in each of the pools.