American Institute of Certified Planners (AICP) Practice Exam

Which population method would use state population forecasts to calculate county population or, following an additional step, could be used to calculate a population projection for a town or city?

1. The Migration and Natural Increase Method

2. The Cohort Survival Method

3. The Symptomatic Method

4. The Ratio (Step-Down) Method

The correct answer is: The Ratio (Step-Down) Method

The Ratio (Step-Down) Method is designed to derive population estimates for smaller jurisdictions, such as counties, towns, or cities, based on larger geographic areas' demographic trends. In this approach, state population forecasts serve as the primary data source, allowing planners to apply a proportional distribution to estimate the population of each county within the state. Once the county populations are determined, further steps can be taken to project the population for smaller towns or cities by using established ratios or historical data that reflects the relationship between the county and its municipalities. This method is particularly effective in scenarios where comprehensive local data may be limited, as it leverages state-level forecasts to achieve more granular estimates. Planners often rely on this stratified approach as it provides a systematic way to anticipate future population shifts relevant to resource allocation, infrastructure planning, and service provision at the local level.