Final answer:
The geographic center is the central point based purely on land area, while the population center is based on where people are actually living, reflecting population distribution changes due to various types of migration.
Step-by-step explanation:
The difference between changes in the geographic center and changes in the population center is rooted in the concepts of location and density. The geographic center refers to the central point of a region based on physical area without regard to population distribution. In contrast, the population center is determined by the distribution of the population within an area; it is the point at which an imaginary, flat, weightless, and rigid map would balance perfectly if all residents were of identical weight.
Movements and changes to these centers occur due to migration, which can affect population density and distribution. This can be voluntary, involuntary, or forced. For instance, the migration of college students to cities for education can shift the population center. There are also historical events like the forced relocation of Native American tribes which have dramatically affected population centers.