What does the Cohort Survival Method primarily rely on for calculating future populations?

The Cohort Survival Method primarily relies on natural increase and net migration to calculate future populations. This method tracks specific cohorts, such as age groups, over time, considering the rates of birth (natural increase) and the movement of people into and out of an area (net migration). By applying these factors to the existing population, planners can make population projections that are grounded in real demographic trends.

The natural increase aspect pertains to the difference between births and deaths within the population, while net migration addresses how many individuals enter or leave the area. Together, they provide a comprehensive view of population dynamics, enabling more accurate forecasts.

Other options do have relevance in population studies but do not form the primary basis of the Cohort Survival Method. Current population data serves as the starting point, but it is the demographic changes captured through natural increase and migration that drive the projections. Similarly, decennial census ratios provide valuable demographic insights but are not the main focus of this method. Basic and non-basic economic activities relate more to economic modeling rather than direct population calculation. Thus, the emphasis on natural increase and net migration makes this method effective for understanding how populations evolve over time.