Recent studies using a methodology for the quantification of cortex in lithic assemblages indicate a deficit in cortical surface area in mid to late Holocene contexts in western New South Wales, Australia. This result is interpreted to reflect the extensive transport of artefacts away from their place of production, thus providing a measure of prehistoric mobility within contexts otherwise noted for technological expediency. Here we provide a further investigation of the observed pattern by testing the null hypothesis that all artefacts were discarded where produced. We calculate the size of stone cobbles required to account for the cortical surface area and volume observed archaeologically and compare these values to the distribution of cobble sizes from the raw material sources from which the assemblages were produced. Results indicate that the very large cobble sizes implied by archaeological cortex proportions are not found in a large enough frequency to reasonably represent the average cobble size chosen for reduction. We conclude that the null hypothesis, that artefacts were discarded where they were produced should be rejected in favour of the original interpretation of cortex loss indicating artefact transport.