Use this estimator for a transparent scenario based on an explicit base population and stated fertility, mortality, migration, or interpolation assumptions.

Variant

Projection or estimation variant of the World Population Prospects.

Name

Conventional name of the variant.

Summary

One-sentence description of the variant's assumptions.

A projection is conditional, not a prediction. Uncertainty increases with the horizon, and discontinuities in migration, boundaries, policy, fertility, or mortality can invalidate the assumed path.

Run multiple scenarios and compare them with a cohort-component projection when the necessary fertility, mortality, and migration schedules are available. Sensitivity ranges are more useful than a single extrapolated path.

• Census Date Midyear Conversion

  Convert a census count taken on an arbitrary date to a mid-year equivalent by exponential interpolation at an assumed constant annual growth rate over the elapsed days between the two dates.

• Headship Rate Household Projection

  Project the number of households with the headship-rate method: multiply each age group's adult population by its age-specific headship rate and sum across groups.

• Postcensal Intercensal Estimator

  Produce a postcensal estimate by the component method (base plus births minus deaths plus net migration since the census) or an intercensal estimate by linear interpolation between two censuses at a stated fraction of the interval.