Enrollment projections are made at various levels, including national, regional, state, school division, and institutional. When statisticians, economists, or mathematicians design enrollment projection models for postsecondary education, certain historical information about enrollment patterns at the elementary, secondary, and postsecondary levels is necessary at the onset of the project. Researchers must also know the current milieu: political issues, economic trends, institutional missions. These same researchers then must select appropriate analytical techniques, scrutinize available information and data, make subjective judgments about enrollment predictions, and incorporate national and statewide demographic trends, including fertility, migratory, and mortality rates.