Various embodiments of a system and method for allocating labor to units processed in a materials handling facility are described. Embodiments may include a labor allocation system configured to receive information associated with a materials handling process that includes handling multiple units. For each unit, such information may indicate a respective pre-handling time period and a respective post-handling time period. The labor allocation system may determine a measure of variability of the pre-handling time periods associated with the units. The labor allocation system may also determine a measure of variability of the post-handling time periods. In response to determining that one of the measures of variability is less than the other, the labor allocation system may determine that each time period associated with the lesser measure of variability is representative of a quantity of labor expended to process a respective unit in accordance with the materials handling process.