We present experimental evidence showing that there is considerable variation between the rates at which scalar expressions from different lexical scales give rise to Upper-Bounded construals. We investigated two factors that might explain the variation between scalar expressions: first, the availability of the lexical scales, which we measured on the basis of association strength, grammatical class, word frequencies and semantic relatedness, and, secondly, the distinctness of the scalemates, which we operationalized on the basis of semantic distance and boundedness. It was found that only the second factor had a significant effect on the rates of scalar inferences.