Demographic and Land Use Models
SANDAG uses a collection of integrated models in its demographic, economic, and land use forecasts.
Demographic, Economic, and Land Use Modeling
The SANDAG suite of regional forecasting models that inform the Regional Growth Forecast (Series 14 Regional Growth Forecast) differs from previous forecasting cycles by improving alignment between regional and subregional data using a disaggregated process. This system ensures that data for small areas sum to larger areas. The collection of models consists of two main components: (1) the San Diego Demographic and Economic model (SanDE), the region-wide forecasting model, and; (2) the Integrated Land Use, Demographic, and Economic Model (iLUDEM), the subregional allocation model. SANDAG continually refines and evaluates these models to incorporate updated techniques and information as necessary.
SanDE is a rates-based model that develops demographic information at the regional level. The purpose of SanDE is to produce a demographic forecast consistent with the future population in the region. The major input to SanDE is the California Department of Finance (DOF) population projections. The DOF periodically produces a population projection series by detailed demographic characteristics for every county in California. The SanDE model then applies cohort-specific rates to the population to arrive at all the socioeconomic detail needed for the forecast.
SanDE produces data about the region’s future economic and demographic characteristics that are then used to generate the variables needed for the Series 14 Regional Growth Forecast. SanDE constructs a variety of data, such as the size and composition of the population, employment by industry, household income, housing units by structure type, occupancy status of housing units, and persons per household.
The iLUDEM process allocates the forecasted regionwide population, jobs, and housing data from the SanDE model to subregional geographies. The iLUDEM process uses the location of housing capacity, along with the location of jobs, to determine the location of future housing units and jobs in the region. The output from this subregional forecast is then utilized by the activity-based model (ABM) for transportation planning purposes.
SANDAG Regional Growth Forecasting Process
Looking Ahead: New Models in Development
SANDAG continues to investigate new tools and methods to support emerging trends in transportation and land use policies, technologies and infrastructure investment. The next generation of SANDAG’s ABM is currently under development, and SANDAG will be developing the next generation land use modeling platform in advance of the 2025 RTP/SCS.
Data Sources
SANDAG’s models require a wealth of data from a variety of sources. These sources are outlined in the table below:
| Data | Source(s) |
|---|---|
| Housing | U.S. Census Bureau, San Diego County Assessor, local jurisdictions |
| Jobs (by industry) | U.S. Bureau of Labor Statistics, California Employment Development Department, U.S. Department of Defense, local jurisdictions |
| Labor market (employment, unemployment, labor force participation) | U.S. Bureau of Labor Statistics |
| Population and demographic characteristics | U.S. Census Bureau, California Department of Finance |
| Price levels and inflation | U.S. Bureau of Economic Analysis, National Association of Realtors |
| Public finance | California Department of Finance |
| Travel times | SANDAG transportation model |
| United States projections | U.S. Census Bureau, and economic projections purchased from private-sector vendor (varies depending on series) |
| Vital records (births, deaths) | California Department of Health |
| Land Use | SANDAG Land Inventory System, San Diego County Assessor, Local Agency General Plans |
