After the 1990s, the Australian coal industry vigorously eliminated two types of task demarcations: (I) the demarcation between production and maintenance stream tasks and (II) the demarcation within the production stream. Using data covering 1985-2005, we estimate the effect of the elimination of these demarcations on productivity, then analyze several explanations for how multi-tasking would affect productivity. The results show that the elimination of 'between' demarcation would increase coal production by 27%, while the elimination of 'within' demarcation has no effect on productivity. Furthermore, the relationship between coal demand uncertainty and the elimination of demarcations is weak. These patterns are inconsistent with a common explanation for how multi-tasking affects productivity: the ability of mines to freely redeploy workers enables mines to fully utilize labor, and to adjust to demand fluctuations. Rather, these results are better explained by the elimination of redundancies: the bundling of 'overlapping tasks' reduces duplication of effort and unnecessary wait time.