Draft – May 4, 2004
Common Procedures for Small Area Forecast
The availability of Census 2000 (Population and Households) will provide a common
data source for most local governments and, in turn, the designated base year for the
Round 7 population and household forecasts. The Small Area Task force has chosen
April 1, 2000 as the beginning.
Year 2000 employment counts from Dun & Bradstreet and local government
employment estimates will provide the base line for the jurisdictional and small-area
employment forecasts, although some jurisdictions may use additional data sources such
as U.S. Bureau of Labor Statistics (BLS), U.S. Bureau of Economic Analysis (BEA), D.C.
Department of Employment Services (DOES), Virginia Employment Commission (VEC)
and Maryland Department of Labor, Licensing, and Regulation, and the Maryland
Department of Planning. Unlike the Census, the Dun & Bradstreet data set is a general
year 2000 figure and does not relate to a specific date in 2000.
The year 2000 will serve as the benchmark to the forecasts which will be made in five
year increments through the 2005 to 2030 period.
Area Systems (Geography):
All forecasts will initially be made at the jurisdictional level and will be later
disaggregated into COG Traffic Analysis Zones (TAZ) using the “2191 Zone” or “Expanded Cordon” Transportation Planning Board (TPB) zone system.
COG Staff has encouraged the use of the 2191 Zone system for creation and submission
of jurisdiction level forecast data. Where this has not been feasible, COG Staff has
developed a series of conversion tables that allow the data to be placed into the
geography of the 2191 Zone system. This is not the most accurate process however as
errors may be introduced when one’s zone’s data is split between two zones during the
conversion process. A good example of the problem is Fairfax County’s Population and Households (Sub-Census Tracts) converted into COG’s “2191 Zone” System. The Sub-
census Tracts are sometimes split between different COG TAZs.
Some of the defects of the “2191 Zone” system include the following:
1. Jurisdictions totals do not equal the sum of the TAZs that comprise a jurisdiction.
Traffic Analysis Zones may not follow jurisdictional boundaries, such as the northern
portion of the city of Fairfax with Fairfax County and areas around the city of Rockville in Montgomery County that have experienced recent annexations.
2. Traffic Analysis Zone 1603 includes the Fairfax County Massey Complex (Fairfax County land). The group quarter population and employment population are included in Fairfax County’s jurisdictional total but are included in TAZ 1603 that comprises most of the city of Fairfax.
3. Takoma Park was part of Montgomery County and Prince Georges’s County. Takoma Park is in now located entirely in Montgomery County. But the “2191 Zone” system has
labeled the eastern part of Takoma Park (COG TAZ 650 and TAZ 648) as part of Prince George’s County. TAZ 650 and 648 should be relabeled as a Montgomery County COG TAZ.
Alternative Forecasts Based on Assumptions (Scenarios):
There is no formal task force designated to review the procedures for the forecast scenarios (low, intermediate, and high) for Round 7. The Cooperative Forecasting and Data Subcommittee decided to make the scenarios responsibility a task for the entire group. (Justin - This is accurate, but I think the Small Area Group should make a
recommendation here. I propose that our Low forecasts represent 65% of buildout, the Medium forecasts represent 80% of buildout, and the High forecasts represent 95% of buildout).
As policy, the Cooperative Forecasting and Data Subcommittee will support three alternative forecast scenarios: low, intermediate, and high. The final Round 7 forecast would be the intermediate forecast.
(Complete this section after we have done the reconciliation)
The sum of the local government employment, population, and household forecasts for each forecast year must be within three percent of the regional econometric model projections for that year. The reconciliation process may take three or four meetings to work out the differences.
1. Average Household Size (AHS): The following U.S. Census Bureau’s definition of household will be used: “The term size of household includes all the people occupying a
housing unit.” Household size can vary from the different housing types such as multi-
family (apartments), townhouse, and single-family. When ever possible task force members applied a different average household size to the different housing types. For
each TAZ, one could use the AHS as reported by Census 2000 at the Census Tract and
Census Block Group level. Approaches to the calculation and application of subcounty
average household size vary among COG jurisdictions. For example, Prince George’s
County applies AHS based on Planning Areas whereas Arlington County bases AHS on
the county’s land use plan.
2. Public Policy: Forecasts should be based on sound land use polices that have been
adopted by a local jurisdiction such as a Comprehensive Plan or Zoning Ordinance. Some
high profile polices may not be “Official,” but their impact in the COG member forecasts should be minimal if possible. Examples of such non land use plan based policies include
the elimination or decline of Section 8 housing, intensifying a downtown area with
100,000 more people in the short term or the construction of more executive or high-end
housing which may yield more taxes for the community but less affordability for the
3. Interest Rate: Lower interest rates can help a sluggish economy - making money
cheaper to borrow. Lower borrowing costs may lead developers to accelerate construction
plans or encourage home sales to existing homeowners and first time homebuyers leaving
the rental market.
4. Pipeline Development: Commercial or residential development that is either proposed
permitted, or under construction. In most cases, “short-term forecasts are based primarily
on pipeline development, i.e., development already planned for construction (Round 6
Cooperative Forecasting Technical Report, Page 28)”. Some projects could be considered
“fast track” such as Fed Ex Field, MCI Center (land use) and the Inter County Connector and Dulles Corridor Rail (transportation).
5. Sewer Capacity: Sewer capacity is one of the major constraints on new development
throughout the United States. COG jurisdictions have documented their approach to the
expansion of sewer capacity as it relates to new development with their individual
forecasts. The ability to levy impact fees or the existence of adequate public facilities
ordinances are noted with jurisdictional level data. Major policy goals associated with
population growth have been assessed including the capacity to meet those goals during
the forecast period.
6. Past Trends: When forecasting development, COG member jurisdictions have largely
used past trends to predict development cycles for development beyond what is already in
the pipeline (approved and pending projects). Key to these assumptions is an
understanding that building occupancy may not occur immediately following
construction. COG small area forecasts include analysis of this time gap and predictions
of how this “occupancy speed” will increase or decrease in the future.
7. Vacancy Rate: The vacancy rate is a short term factor effecting the forecast as it is a
ratio of occupied dwelling units to unoccupied dwelling units. The U.S. Census Bureau
distinguishes between a Rental Vacancy Rate and a Homeowner Vacancy Rate. An
average vacancy rate (a housing unit is vacant if no one is living in it) is applied to the
dwelling unit count in order to determine the total number of households (i.e. occupied
housing units). Much like Average Household Size, vacancy rates will vary between
housing types and many member jurisdictions have assigned standard vacancy rates
based on housing type.
8. Regional Housing Market: When examining new home sales region wide, if a slow
down in residential construction occurs in one part of the region – one could assume the
slow down would impact other areas of the region. Housing polices of one jurisdiction
9. Infill Development: New assumptions must be made to existing developed areas based
on new development goals in member jurisdictions’ general land use plans.
(Opportunities for redevelopment, revitalization and potential for intensifying
development in transit station areas)
10. Development Regulation/Development Practice: Development policies that either
encourage or discourage development through impact fees, proffers, incentives, or other
land use tools vary among jurisdictions. Key policies included the expiration dates for
building permits, affordable housing provisions, or regulations that require the
development of commercial space in tandem with residential construction. Jurisdiction
level notes address these details as they relate to forecast data. Development practice also
varies among jurisdictions. Where these practices affect forecast numbers.
11. Group Quarters: We should examine college and prison construction at site-specific
locations to determine expansion plans that will add to the existing group quarter’s
population. As the population continues to age – there will be a greater demand for
retirement homes and assisted living facilities. The homeless population is counted as a
group quarters population (shelter location). The Small Area Task Force will need to
coordinate with the Key Factors group to discuss their assumptions for forecasting the
group quarter population.
12. Employment: Forecasts of employment include vacancy rates and allotment of square
footage per employee. Because employment data comes from a variety of sources
(unlike the Census based population and household forecasts) these key factors vary
greatly among jurisdictions. Generally, outer jurisdictions have higher square footage per
employee than inner jurisdictions. COG members have discussed the application of
uniform numbers for square footage per employee but have decided that the variation
among area commercial environments does not support such a streamlined approach.
In addition to total employment figures for each jurisdiction, COG member forecasts
include TAZ level employment totals along with employment by type for office, retail,
industrial and “all other” job categories. In the past, COG included an institutional land
use category. The model no longer uses the institutional category. If a jurisdiction
submits institutional employment, COG will add the institutional employment with the
office land use category.