United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park. NC 27711
Research and Development
EPA/600/SR-93/067 August 1993
Project Summary
Economic Growth Analysis
System (E-GAS)
Teresa Lynch and Randy Randolph
The two-volume report describes the
development of, and provides Informa-
tion needed to operate, a prototype Eco-
nomic Growth Analysis System (E-GAS)
modeling system. The model will be
used to project emissions inventories
of volatile organic compounds (VOCs),
oxides of nlltrogen (NOx), and carbon
monoxide (CO) for ozone nonattalnment
areas and Regional Oxidation Model
(ROM) modeling regions.
The report details the design and de-
velopment of the E-GAS system and
Includes detailed descriptions of the
workings of the E-GAS computer mod-
eling software and Its relationships with
Internal modeling software components
and external software.
The system Is an economic and ac-
tivity forecast model that translates the
user's assumptions regarding regional
economic policies and resource prices
Into Source Code Classification (SCC)
level growth factors for VOCs, NOx,
and CO. The report provides E-GAS
users with sufficient background infor-
mation to define and calibrate the E-
GAS model, as well as the procedures
and syntax necessary to operate the
system. The organization of the user's
manual Is determined by the process
used In operating the system, provid-
ing Images of sample screens as well
as text.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle Park, NC, to announce key find-
ings of the research project that Is fully
documented In two reports (see Project
Report ordering Information at back).
Introduction
On November 15, 1990, the Clean Air
Act Amendments (CAAA) of 1990 were
signed into law. The CAAA require that
extreme, severe, serious, and multi-state
moderate ozone nonattainment areas use
photochemical grid modeling to demon-
strate future attainment with the ozone
national ambient air quality standard
(NAAQS) [Section 182(e)(2)(A)]. In addi-
tion to photochemical grid modeling, the
CAAA require that moderate, serious, se-
vere, and extreme ozone nonattainment
areas submit reasonable further progress
(RFP) inventories demonstrating a 15%
reduction in emissions from 1990 to 1996
[Section 182(b)(1)(A)]. Further, RFP in-
ventories for serious, severe, arid extreme
areas must include demonstration of a 3%
reduction (averaged over 3 years) from
1996 until attainment is achieved [Section
182(c)(2)(B)].
Section 182(b)(1 )(A) of the CAAA speci-
fies that the 15% redirection from baseline
emissions accounts for any growth in emis-
sions after 1990. A key component of the
RFP inventories and photochemical grid
modeling demonstrations will be the devel-
opment of credible growth factors for the
existing inventories.
Since growth in source emissions
largely depends on the amount of eco-
nomic activity growth in an area, a consis-
tent set of growth factors requires forecasts
using consistent Gross National Product
(GNP) forecasts and a consistent method-
ology for estimating economic activity in
Urban Airshed Model (UAM) and ROM
modeling regions. The need for consistent
economic growth factors, however, must
be satisfied in a way that allows states to
use their own estimates of national and
regional economic activity. E-GAS is an
economic and activity forecast model which
satisfies both of these standards.
The existing inventories for RFP dem-
onstration and photochemical modeling will
be housed in the Aerometric Information
Retrieval System (AIRS). E-GAS can be
applied to AIRS inventories for the devel-
opment of emission projections to 2010,
when extreme areas must reach attain-
Printed on Recycled Paper
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ment. State users can create custom GNP
forecasts and may modify input assump-
tions for the regional models in E-GAS.
The system also allows EPA users to de-
velop VOC, NO,, and CO growth factors
using a single GNP forecast, providing
baseline emission growth estimates for
comparison with growth factors submitted
by the states.
The nonattainment areas modeled were
chosen on the basis of their nonattainment
designation. All serious, severe, and ex-
treme areas were modeled, as were multi-
state moderate areas. These areas, their
designations and area definitions, were
announced in the November 6,1991, Fed-
eral Register
To minimize both the number and run
time of the models in E-GAS, eight models
were developed. Separate models were
developed for EPA Regions 1, 4, 5, 6,7,
and 9. In addition, models that combine
the areas in EPA Regions 2 and 3 and
EPA Regions 8 and 10 were developed.
Each model includes all extreme, severe,
serious, and multi-state moderate areas,
as well as each state and partial state in
the region.
E-GAS is a menu-driven system that
guides the user through a series of screens
that collect information for adapting the
model to the user's needs. User input is
limited to selecting menu items and setting
parameters by entering data in text boxes.
The E-GAS modeling system contains
three tiers. The first tier includes available
national economic forecasts that are used
to drive the regional economic models.
The second tier includes regional economic
models for the (JAM modeling areas, as
well as the states in the ROM modeling
regions. The third tier estimates fuel con-
sumption, physical output, and Vehicle
Miles Traveled (VMT) based on the sec-
ond tier's regional economic forecasts. The
tiers must be sequentially executed, since
data are created by and passed from early
tiers for transfer to later tiers. The three-
tiered structure of E-GAS allows users flex-
ibility in modelling. While tiers must be run
before proceeding to later tiers, the system
allows the models to be rerun at the user's
discretion. For example, users may run a
variety of national models before perform-
ing regional modelling on the last national
model run.
The National REMI Model allows the
user to create a national-level growth pro-
jection. It is Tier 1 of the three-part process
of creating estimated growth factors; it gen-
erates data to drive the Regional REMI
Model (Tier 2). This tier may be rerun any
number of times before proceeding to Tier
2.Two national forecasts are available for
the user: Bureau of Labor Statistics (BLS),
and Wharton Econometric Forecasting As-
sociates (WEFA).
The Regional REMI Model allows the
user to develop a regional growth simula-
tion. This is Tier 2 of the three-part process
of creating estimated growth factors; it gen-
erates data to drive the Growth Factor
Module (Tier 3). In the E-GAS model, there
are over 100 regular economic policy vari-
ables, translator variables, and population
variables that can be adjusted. Changing
these variables allows the user to simulate
the economic impact of anticipated
government policy changes, market
changes, or other exogenous changes to
the regional economy. These variables are
accessed from the REMI EDFS-14 model
and offer scenarios for changes in tax
rates (corporate profit tax, equipment tax,
investment tax, personal income tax, and
property tax), costs (including relative pro-
duction cost, import cost, and export cost),
wage rate, employment transfer payments,
purchasing power, and final demand. This
tier may be rerun any number of times
before proceeding to Tier 3.
The Growth Factor Module is the third
tier where growth factors are generated
and written to files in the \EGAS
subdirectory. This module translates
changes in the economic activity levels of
the most recent regional forecast to growth
factors for physical output, fuel consump-
tion, and VMT. These growth factors will
be developed for two-, three-, and four-
digit Standard Industrial Classification (SIC)
levels depending on available data for de-
veloping and disaggregating the factors.
These SIC-level growth factors will be
matched with SCC codes. The user is
given a choice of file formats as either the
EPS format or as an ASCII text file. The
file is output by year, county level, and
SCC code.
E-GAS Reference Manual
The Reference Manual provides back-
ground information on the design, devel-
opment, and implementation of the E-GAS
system, as well as information concerning
the execution of the system itself. Chapter
1 provides an overview of the system to
the user as well as discussions of basic
system design and development consider-
ations. Chapter 2 discusses the CAAA re-
quirements related to the use of
photochemical grid modeling in demon-
strating future NAAQS attainment and the
submission of rate of progress plans that
will demonstrate how an area will achieve
the 15% reduction in VOC emissions
by 1996, compared to the use of E-GAS.
Chapter 3 discusses the current EPA emis-
sions projection guidance and its relation-
ship to E-GAS. Chapter 4 explains the role
and use of national and regional economic
forecasts in E-GAS. Chapter 5 discusses
how fuel choice is forecast within E-GAS.
Chapter 6 discusses how physical output
is estimated within E-GAS. Chapter 7 ex-
plains the methodology used within E-GAS
to forecast VMT. Chapter 8 explains
CROSSWALK, the final component of E-
GAS. The CROSSWALK component as-
signs growth factors from the other E-GAS
modules to point, area, and mobile source
classification codes (SCC). Appendix A
lists the Bureau of Labor Statistics codes
and SCC matches used within the CROSS-
WALK component of E-GAS. Appendix B
provides an example of the CROSSWALK
output files.
E-GAS User's Guide
The User's Guide pilots the user through
the E-GAS system. Chapter 1 introduces
the terminology used with the system as
well as the syntax and format of the pro-
gram and user guide. Chapter 2 discusses
the use of E-GAS by explaining the logical
progression of the program, presenting
sample screens, providing explanations of
input formats, and describing the E-GAS
utilities found throughout the system. Chap-
ter 3 describes the role of national eco-
nomic models in E-GAS and the two options
available to the user. Chapter 4 explains
the general function of E-GAS's policy vari-
ables; it then describes the specific vari-
ables while explaining their input. Chapter
5 describes the role of model suppressions
in E-GAS and describes all suppressions
available to the user. Chapter 6 describes
the operation of and data required for the
E-GAS National Model (Tier 1). Chapter 7
provides similar descriptions of the Re-
gional Model (Tier 2), and Chapter 8 de-
scribes the third tier, the Growth Factor
Module. Chapter 9 identifies contacts for
further information regarding the operation
of E-GAS and the logic of the system.
Basic Hardware Requirements
The program has been designed for an
IBM-compatible personal computer envi-
ronment. The system requires the follow-
ing minimum hardware configurations:
• IBM 80386 or 100% compatible per-
sonal computer
Math coprocessor
100 megabytes of available fixed
disk storage
VGA graphics capabilities
DOS 5.0 or higher
51/4 or 31/2 in. floppy disk drive.
&U.S. GOVERNMENT PRINTING OFFICE: 1993 - 750-071/80042
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T. Lynch and R. Randolph are with TRC Environmental Corp., Chapel Hill, NC
27514..
£. Sue Klmbrough is the EPA Project Officer (see below).
The complete report, entitled "Economic Growth Analysis System (E-GAS)," &
made up of two volumes and eight sets of computer disks.
The volumes are the Reference Manual, EPA/600/R-93/067a (Order No. PB93-
183408; Cost: $36.50), and the User's Guide, EPA/600/R-93/067b (Order No.
PB93-183416; Cost: $19.50).
The order numbers and costs of the sets of disks are:
EPA&00/R-93/067C—Order No. PB93-505477; Cost: $140.00
EPA/600/R-93/067d—Order No. PB93-505485; Cost: $140.00
EPA/600/R-93/067e—Order No. PB93-505493; Cost: $140.00
EPAfiOO/R-93/067f—Order No. PB93-50S501; Cost: $140.00
EPA/600/R-93/067g—Order No. PB93-505519; Cost: $140.00
EPAtfOO/R-93/067h—Order No. PB93-505527; Cost: $140.00
EPA/600/R-93/067i—Order No. PB93-505535; Cost: $140.00
EPA/600/R-93/067J—Order No. PB93-50S543; Cost: $140.00
The complete set (Order No. PB93-505489; Cost: $950.00) consists of the two
volumes and eight sets of computer disks mentioned above.
All prices are subject to change. This report will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-93/067
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