Floating population
Floating population is a terminology used to describe a group of people who reside in a given population for a certain amount of time and for various reasons, but are not generally considered part of the official census count.
A population is usually broken down into two categories—the residents, who permanently stay in an area for a considerable amount of time and are part of the official population count, and the floating types, who are in the area but do not live there permanently and are not considered part of the official census count.