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Scenario Building

Scenario Building. The most critical part of the projection process is the delineation of a Projection Scenario. Projection Scenario : The set of assumptions specified for the area being studied and for the projection method(s) utilized, across the projection interval.

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Scenario Building

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  1. Scenario Building • The most critical part of the projection process is the delineation of a Projection Scenario. Projection Scenario: The set of assumptions specified for thearea being studied and for the projection method(s) utilized,across the projection interval. • The projection scenario in many ways shapes the projections (and ultimately the forecast) generated. For all practical purposes: The Scenario is the Forecast. • There are many types of assumptions that must be laid out when undertaking population forecasting: --Universal Assumptions (No wars, no catastrophic events) --Method-Based Assumptions (Future mortality rates) --Local Area-Based Assumptions (Future of fishing industry) --Regional-Based Assumptions (Florida’s future growth)

  2. Scenario Building Techniques • “They can be based on information gathered from monitoring, brainstorming, analogies, modeling or other activities. They should be developed rigorously and thoughtfully…” (Isserman) • Typical aids utilized in developing useful scenarios: 1) Historical Studies --Development of the area, Local history --Past rates of change in population, housing starts, births, etc. --Local planning initiatives, Policy environment 2) Consultation with Local Experts --Planners --Civic Leaders, both private and public 3) Choice of Control Units --Nearby counties --State • Successfully developing a scenario is an inclusive process: --Group inclusive --Community inclusive --Interest inclusive

  3. Specifying Assumptions • All projections are predicated on assumptions. These must be specified so that: 1) producers of the projections can determine the internal and external consistency of their projections/forecasts 2) consumers of the projections can understand the underlying logic/decisions behind these projections/forecasts • Once the historical studies have been undertaken, interviews completed, and control units have been studied, it is time to provided a detailed specification of the assumptions. • These should be as detailed as possible, laid out along the four assumption specification areas (Universal, Method-Based, Local Area-Based, and Region-Based assumptions). • These can be included in a separate section of the projection document (relatively rare) or included throughout the document in appropriate sections (history in the history section, method-based in the methods section(s), and so on), which is more common.

  4. A Forecast Scenario for Franklin County • For URP5261 in 2003, the class contributed to the development of a population forecast for Franklin County (FC). • FC is another Panhandle county soon to be transformed by St. Joe and this forecast was a primary input into the development of a Comprehensive Plan Update. • As part of this project, a scenario was developed that identified: 1) major factors contributing to population growth in FC in the period 2000-2030 2) major factors likely to limit population growth in FC in the period 2000-2030 • These factors were identified through a review of existing studies/documents, interviews with local experts, review of popular media (newspaper), and a review of other Panhandle county growth experiences in recent decades

  5. FC Forecast Major Assumptions 1) No wars, sustained and long-term economic recessions, or natural disasters will come to the region and devastate the county. 2) SummerCamp and other in-development projects will be built out by 2010. 3) A state prison will be funded by the state and be built by 2010 in the county. This prison will bring 1,200 new ‘residents’ to the community in the form of prisoners. 4) Additional large-scale residential projects will be developed between 2010-2030. It was assumed that an additional 1,750 new residential units in master planned communities will be completed by 2020 followed by an additional 2,500 units between 2020-2030.

  6. Factors Promoting Growth in Franklin Co. • Historic Population Growth in the County • Continued Growth of the State and Region • Emergence of Florida’s Great Northwest as a Successful “Brand” for the Region • Current Development Activity by St. Joe and Other Developers • Future Development Activity by St. Joe and Other Developers • Demographic Factors • New State Prison in Franklin County

  7. Factors Limiting Growth in Franklin Co. • FC’s Regional Location • Infrastructure Issues • Large Public Land Holdings • St. Joe Land Holdings • The State’s Role in Limiting Development in FC • Anti-Development County Culture

  8. Visualizing Franklin County’s Scenario

  9. Franklin County Forecasts Using Different Methods

  10. The Franklin County Forecast

  11. Example: Franklin County’s Combined Forecast

  12. Evaluating Forecasts • The three typical ways of evaluating a forecast are: 1) Accuracy: Correctness of the forecast 2) Validity: Correctness of the model and causality 3) Constancy: Validity over time and across situations • But, forecasts are invariably incorrect, so maybe we should assess them on slightly different dimensions: 1) Methodologically Sound --The forecast makes sense relative to the characteristics and assumptions of the methods 2) Internal Consistency --The forecast makes sense compared to historical demographic patterns --The forecast makes sense compared to local socioeconomic/ cultural characteristics 3) External Consistency --The forecast makes sense compared to contextual and/or comparison areas

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