There are various synonyms for the phrase "per unit of population." Some common alternatives include "per capita," "per head," and "per person." These phrases refer to the average or individual amount of something in relation to the total number of people in a given population. They are often used in statistics or economics to analyze and compare data on a per-person basis. For instance, per capita income measures the average income per person in a particular region or country. Similarly, per capita healthcare spending refers to the amount of money spent on healthcare per person in a population. These synonyms all serve the same purpose, providing a way to measure or analyze data relative to population size.