A plastic closure embodying the principles of the present invention comprises a closure cap having a top wall portion, and an annular skirt portion depending from the top wall portion. The skirt portion includes an internal thread formation for threaded engagement with the external thread formation of an associated container. In order to facilitate high-speed application, and minimize the use of polymeric material, the closure is configured to exhibit a variation in retention force which decreases in a direction away from the top wall portion of the closure cap.