In volcanic fields, the location of an eruptive vent controls the hazards, their intensities, and ultimately the impact of the eruption. Estimates of where future eruptions are likely to occur inform evacuation plans, the (re)location of vital infrastructure, and the placement of early-warning monitoring equipment. Current estimates assume that locations with more past-vents are more likely to produce future-vents. We provide the formulae for an alternative hypothesis of magma depletion.