If you are not overstaffed

then you are not adequately staffed, unless you can guarantee that none of your employees will ever take vacation, get sick, have family members die, or have any personal emergencies. Being merely "adequately staffed" is a prime strategy in the Ostrich School of Management, in which the higher-ups stick their head in the sand, so to speak, and hope that dedicated employees will bail them out of their short-sightedness.