Demography is the study of a population, the total number of people or organisms in a given area. Understanding how population characteristics such as size, spatial distribution, age structure, or the birth and death rates change over time can help scientists or governments make decisions. For example, knowing how lion populations have increased or decreased over a period of time can help conservationists understand if their protection efforts are effective while knowing how many seniors or children live in a particular neighborhood can shape the type of activities scheduled at the local recreation center. page 