Oregon -- Population -- Statistics, Demographic surveys -- Oregon
This document is to accompany the coordinated population forecasts and their corresponding reports prepared by the Population Research Center (PRC).
Developing long-term coordinated population forecasts for a county and its sub-areas (UGBs and areas outside UGBs are referred to sub-areas in this document), requires these main stages: 1) compiling and evaluating historical and recent data to ascertain demographic characteristics and trends in the study area and to obtain a population base from which the forecasts may be launched; 2) making assumptions about the future and adjusting the data or rates in the forecasting models (calibrating the models) to incorporate predicted rates or trends; and 3) reconciling, or adjusting the forecasts so the sum of the sub-area forecasts is consistent with the forecast for the county total.
We first develop population projections and then we make adjustments to these projections in order to produce population forecasts. Population projections are developed by extending historical and current demographic and housing trends into the future. Forecasting population requires that assumptions be made about future population change, and adjusting the projection models to account for circumstances that perhaps skewed past trends or may affect future change. Such circumstances in the past could be a building moratorium or the opening of a new group quarters facility. Events affecting future change would be, for example, planned future housing development that is higher than usual, a foreseen change in an area’s physical ability to accommodate growth (buildable land available is approaching capacity or improvements to infrastructure are underway), anticipated changes in the economy (the location of a new employer or the upswing or downturn of the economy in general), or an expected change in the local population and household composition (age, ethnicity, and average household size).
Portland State University. Population Research Center, "Methods and Data for Developing Coordinated Population Forecasts" (2015). Publications, Reports and Presentations. 32.