How do population projections typically predict changes in populations?

Population projections typically predict changes in populations by examining current demographic data. This approach involves analyzing various data points, such as birth rates, death rates, age distribution, and migration patterns, to present a comprehensive view of the population's dynamics at a particular time. Current demographic data allows for a more accurate understanding of the population structure, which can then be used to forecast future changes in population size and composition.

In addition to current data, projections often consider historical trends to inform the future; however, the accurate reflection of the present conditions is crucial for making reliable predictions. This multi-faceted approach uses the latest information to account for various influencing factors, thereby providing a better estimation of how the population is likely to change over time.

The other options, while they can contribute to understanding population dynamics, do not encompass the comprehensive methodology typically utilized in population projections as well as examining current demographic data does.