Identifiable Victim Affect
A single death is a tragedy; a million deaths is a statistic.
The Identifiable Victim Affect is the psychological bias to empathize more with a smaller number of people than a larger number of people.
People are more likely to give to charity when you only name a single person in need, rather than several. This is a studied phenomenon. When you describe two victims, results get worse. If you describe dozens of victims, donations decline further. If you give a statistic covering thousands of people, donations are at their worst.
A smaller group is actually easier to relate to because you can be drawn to idiosyncratic character traits. When describing a larger group of people, by comparison, we are compelled to talk about the traits that are common among everyone in the group, and this list of traits as the group grows. The personification of a large, will thus have a limited number of character traits.