2-i

CHAPTER 2. ANALYTIC FRAMEWORK

TABLE OF CONTENTS

2.1 OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

2.2 MARKET AND TECHNOLOGY ASSESSMENT . . . . . . . . . . . . . . . . . . . . . 2-3

2.3 IDENTIFICATION & SCREENING OF DESIGN OPTIONS . . . . . . . . . . . . . 2-4

2.4 ENGINEERING ANALYSIS (PRICE EFFICIENCY RESULTS) . . . . . . . . . . 2-4

2.5 LIFE-CYCLE COST (LCC) ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2.6 CONSUMER SUB-GROUP ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.7 SHIPMENTS ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

2.8 NATIONAL ENERGY IMPACTS (NES) ANALYSIS . . . . . . . . . . . . . . . . . . 2-8

2.9 MANUFACTURER IMPACTS ANALYSIS (MIA) . . . . . . . . . . . . . . . . . . . . 2-9

2.10 UTILITY IMPACTS ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

2.11 ENVIRONMENTAL ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

2.12 NET NATIONAL EMPLOYMENT ANALYSIS . . . . . . . . . . . . . . . . . . . . . . 2-10

TABLES

Table 2.1 Summary Characteristics of the Baseline Models for Three Water Heater Product

Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

FIGURES

Figure 2.1 Framework Flowchart for Water Heater Energy Efficiency Analysis . . . . . . . . 2-2
2-1

CHAPTER 2. ANALYTIC FRAMEWORK 

2.1 OVERVIEW

In the water heater rulemaking, DOE has used the following steps and analyses. These are

summarized in the framework diagram shown in Figure 2.1 below. The numbers in the lower righthand corner of the boxes refer to the relevant chapter in this Technical Support Document. Solid

lines in the flowchart indicate inputs and outputs; dotted lines, on the other hand, follow the path of

intermediate results from one part of the analysis to another. The steps involved in the process in

a roughly sequential order are:

• Market and Technology Characterization

• Identification and Screening of Design Options

• Engineering Analysis

• Life-Cycle Cost Analysis

• Consumer Sub-Group Analysis

• Shipments Analysis

• National Energy Impacts (NES) Analysis

• Manufacturer Impacts Analysis (MIA)

• Utility Impacts Analysis

• Environmental Analysis

• Net National Employment Analysis

• Regulatory Impact Analysis
2-2

Figure 2.1 Framework Flowchart for Water Heater Energy Efficiency Analysis
2-3

2.2 MARKET AND TECHNOLOGY ASSESSMENT

The objective of the Market and Technology Assessment is to develop baseline models and

the list of potential design options for each of the electric, gas-, and oil-fired water heater product

classes. The choice of baseline models and design options is from information and analysis regarding

the market situation of water heaters in the U.S. The gas-fired product class includes water heaters

fueled by both natural gas and liquified petroleum gas (LPG) because they are constructed almost

identically. With respect to costs, however, they are treated separately, having different

manufacturing costs, markups, retail prices, and fuel price structures. The general characteristics of

the baseline model for each of the three primary product classes of water heaters analyzed are

provided in Table 2.1 below.

Table 2.1 Summary Characteristics of the Baseline Models for Three Water Heater

Product Classes

Electric Natural Gas & LPG Oil-Fired

Tank Volume 50-gallon (190-liter) 40-gallon (150-liter) 32-gallon (120-liter)

Tank Type Glass-lined steel Glass-lined steel Glass-lined steel

Insulation 1.5-inch (3.8 cm)

polyurethane foam

insulation blown with

HCFC-141b

1-inch (2.5 cm)

polyurethane foam

insulation blown with

HCFC-141b

1-inch (2.5 cm) polyurethane foam

insulation blown with HCFC-141b

Input Rating 4500 W 40,000 Btu/hr (11,700 W) 0.65 gallons per hour (2.5 liters/hr) or

90,000 Btu/hr (26,000 W)

Recovery

Efficiency

(RE)

0.98 0.76 0.75

Energy

Factor

0.86 0.54 0.53

Analysis

Tools

WATSIM, a computer

simulation model of

electric water heaters

TANK, a computer

simulation model of gasfired water heaters

A simplified water heater analysis

model (WHAM), based on the DOE

24-hour test procedure, is an equation

to calculate average daily energy

consumption using the RE, stand-by

heat loss coefficient (UA), and rated

input (Pon).

Other Two interlocked heating

elements

Bottom-fired with center

flue

Bottom-fired with center flue. The

baseline model uses an intermittent

ignition system. The burner motor,

which powers both the blower and oil

pump, is rated at 282W.
2-4

2.3 IDENTIFICATION & SCREENING OF DESIGN OPTIONS

The first step in the rulemaking process is screening of design options. The purpose of

screening is to identify those design options that the Department will consider for the engineering

analysis. The screening analysis also discusses the criteria for eliminating certain design options

from further consideration. On July 15, 1996, the Department issued the Process Improvement

(Interpretive) Rule1 which establishes the factors DOE uses for screening design options. The factors

are as follows:

` Technological feasibility;

` Practicability to manufacture, install, and service;

` Adverse impacts on product utility or product availability;

` Adverse impacts on health and/or safety.

2.4 ENGINEERING ANALYSIS (PRICE EFFICIENCY RESULTS)

The results of the Engineering Analysis, termed “price efficiency results”, demonstrate the

increased cost and efficiency due to design options and combinations of design options within each

product class of water heaters. To arrive at the price efficiency results, the Engineering Analysis uses

computer simulation models and other analytical methods (see Table 2.1 under “Analysis Tools”)

to investigate the efficiency improvements of a design option and combinations of design options.

The models and analytical methods are based on DOE’s test procedure for residential water heaters.

All prices, including Annual Energy Outlook 20002

 (AEO2000) energy prices, are national averages.

For this analysis, we obtained manufacturers’ cost data for the design options from Gas Appliance

Manufacturers Association (GAMA) and industry consultants. Additionally, we questioned retailers

and installers around the country to obtain retail prices and installation costs of water heaters. The

results of the engineering analysis are used to select and order the combination of design options for

the Life-Cycle Cost Analysis.

The design options are listed in ascending order by payback period. The payback period

measures the amount of time needed to recover the additional consumer investment in increased

efficiency through lower operating costs. DOE test procedure conditions and the 1998 national

average energy price are used in the payback calculation. 

The following technological changes are included in the 2003 baseline model:

• Insulation blowing agent: The U.S. EPA is phasing out HCFC-141b on January 1, 2003.

As a result, water heater manufacturers will have to use an alternative foam insulation

blowing agent. One of the leading alternative blowing agents, HFC-245fa, was chosen

for analysis by DOE.
a

Water heaters fueled by natural gas and LPG are considered as one product class from the point of view of physical

and efficiency characteristics. They are treated separately with respect to manufacturing cost, markup, retail price,

and fuel price in the Life-Cycle Cost and subsequent analyses.

2-5

• Flammable-Vapor Ignition Prevention Design: The Consumer Product Safety

Commission initiated a safety design program for natural gas and LPG water heatersa

 to

prevent ignition of flammable vapors. The water heater industry and the Gas Research

Institute (GRI) established a voluntary program to develop a test procedure and burner

designs resistant to ignition of flammable vapors. Several manufacturers joined the Water

Heater Consortium to pool design and developmental resources. As a result of discussions

with this consortium, DOE used a placeholder value of $35 as additional cost for designs

to prevent ignition of flammable vapors. In this analysis, the extra $35 is applied to the

manufacturer cost of all design options for natural gas and LPG water heaters, including

the 2003 baseline design.

For high-efficiency natural gas and LPG water heaters, venting may pose problems. We

assumed Type-B vent connectors may be required in 25% of homes with heating degree days (HDD)

above 5000 when recovery efficiency (RE) is 78% or above. Additional modifications, including

the relining of masonry chimneys, may be needed in 25% of homes with masonry chimneys and

HDD above 5000 when an 80% RE is reached.

2.5 LIFE-CYCLE COST (LCC) ANALYSIS

The LCC analysis determines the life-cycle cost and the cumulative payback for consumers

for a variety of design options on residential water heaters. Life-cycle cost represents the present value

of the consumer’s cost of purchasing and installing a water heater and operating it for its lifetime. To

account for all the variability and uncertainty among consumers, the analysis is done 10,000 times

from a weighted sampling of 3,911 households with individual water heaters from the Residential

Energy Consumption Survey (RECS) database.3

 In addition to the variety of consumers, other inputs

for the analysis are also represented as samples drawn from a range of values. In this way, the

analysis accounts for the full range and variability of characteristics related to residential hot water

use.

• To account for uncertainty and variability, the LCC model uses Monte Carlo simulations

to perform the analysis. The uncertainty and variability in the model’s inputs are specified

using probability distributions. The Monte Carlo simulation then randomly samples from

the probability distribution for each input within the model to calculate the outputs. This

is done 10,000 times for each fuel. The distribution of the values calculated for the model

outcome therefore reflects the probability that those values would occur in the general

population. This technique provides insight into the likelihood of possible outcomes. 

• An importance analysis is also conducted which shows the relative contribution of each

of the inputs to the total range of outputs. 
a

Average energy prices for a consumer are derived by dividing annual energy costs by annual energy consumption.

2-6

Much of the input for this analysis comes from the Engineering Analysis (or the Price

Efficiency Results). Other major input is from a database of water heater specifications and costs and

from distributions of manufacturing costs from GAMA and consultants. The results of the LCC

Analysis are used by the Department to select the trial standard levels used in the later stages of

analysis and decision-making. The outputs are used by the National Energy Impacts Forecast analysis

and the Utility and Environmental analyses. Assumptions made in the LCC analysis are:

• The combinations of design options are taken directly from the Engineering Analysis.

• The estimate of factory cost for the baseline models and the range of incremental cost of

design options were supplied by GAMA. For a few design options, GAMA was unable

to supply estimates of manufacturer costs; consultants familiar with the water heater

industry were, therefore, hired to supply the data.

• To obtain markups, the retail prices for existing baseline models were divided by GAMAsupplied manufacturing costs. A different markup was calculated for each sampled house,

but was kept the same for all design options applied to the water heater in that house.

Average markup varies by fuel type and tank size.

• GAMA-supplied estimates of factory costs were for typical size tanks only. The range of

factory costs was estimated for water heaters with other size tanks by adding or

subtracting the material costs for different amounts of steel, for both the jacket and the

tank, and for different amounts of foam insulation.

• The energy consumption in the LCC analysis was calculated using the Water Heater

Analysis Model (WHAM). The energy parameters used by WHAM—RE, UA, and

Pon—are from the simulation models used in the Engineering Analysis. The temperatures

and average daily hot water use were calculated for individual households in the analysis

according to algorithms explained in the TSD.

• For this analysis, the price of baseline models was taken from the LBNL Water Heater

Price Database. The baseline models were defined as those with six-year manufacturer

warranties or less.

• Installation of larger diameter water heaters under new standards may not be possible in

all circumstances. To account for this, in households of less than 1,000 ft2

 in which the

water heater is in a conditioned space, we assigned the next smaller standard size water

heater and then adjusted the setpoint to ensure delivery of an equal amount of hot water.

• Installation costs were also taken from the LBNL Water Heater Price Database. In

addition to the actual costs of installing water heaters, delivery, removal, and permit fees

were also included. Typical costs for miscellaneous parts used in installing a water heater,

such as pipe fittings, were also added. 

• Four fuels were analyzed: electricity, natural gas, LPG, and oil.

• The household characteristics remained constant over time.

Previous analyses of the life-cycle costs of consumer energy savings possible from appliance

energy-efficiency standards were based on average energy prices.a

 Using marginal energy prices in
a

 Marginal prices as discussed here are those prices consumers pay (or save) for their last units of energy used (or

saved). Marginal prices reflect a change in a consumer’s bill (that might be associated with new energy efficiency

standards) divided by the corresponding change in the amount of energy the consumer used.

2-7

these analyses is more theoretically sound.a In April 1998, the Advisory Committee on Appliance

Energy Efficiency Standards delivered a letter to the Secretary of Energy recommending, among other

things, that DOE should replace the use of national average energy prices with the full range of

consumer marginal energy rates in its life-cycle cost analyses. Because neither published nor readily

available data existed for consumer marginal energy prices, a major research effort was required to

derive consumer marginal energy prices.4, 5

Data from DOE’s Energy Information Administration’s (EIA) 1997 RECS are used to

calculate marginal energy prices for residential appliance owners. We estimated consumer marginal

energy prices directly for each RECS household used in the LCC and Consumer Sub-Group analyses

by calculating the slopes of the regression lines relating customer bills to customer usage. For

electricity, the slopes of the regressions for four summer months (June-September) and, separately,

for the remaining ("non-summer") months, were calculated. For natural gas, the data were split into

seasons in a manner parallel to electricity data. The "peak" winter season was defined as those billing

periods whose midpoint fell in any of the following four months: November, December, January,

February. The remaining eight months constitute the non-winter season.

2.6 CONSUMER SUB-GROUP ANALYSIS

The Consumer Sub-Group Analysis examines the economic impacts from possible revisions

to water heater energy-efficiency standards on different population groups of consumers. The analysis

determines whether or not a particular segment of consumers would be adversely affected from

different trial standard levels in terms of increased life-cycle cost. The fraction of population that

would benefit is calculated. The mean life-cycle cost change is also estimated. Of particular interest

is the potential effect of standards on households with low-income levels and on seniors-only

residences—two consumer sub-groups of interest identified by stakeholders. These two consumer

sub-groups are identified from the RECS public use database. Inputs, analysis method, and

assumptions are the same as those used in the LCC analysis.

2.7 SHIPMENTS ANALYSIS

The Shipments Analysis produces two quantities: (1) the total number of water heaters of all

fuel types that are purchased in a year and (2) the market share by fuel type for water heater

shipments. A different market share distribution is expected for each of the trial standard levels. The

output from the Shipments Analysis allows a national cost/savings analysis to be performed for each

proposed trial standard level (see National Energy Impacts).
2-8

Water heater shipment forecasts by fuel type are used primarily as input in the National

Energy Impacts Analysis. Shipment forecasts are also used by the Manufacturing Impacts analysis.

The assumptions for the analysis are:

• Equipment costs are from the LCC analysis.

• Fuel price projections are from Annual Energy Outlook 2000 (AEO2000)

2

 and the 2000

Edition of the GRI Baseline Projection (GRI2000).6

• The only two drivers for total water heater shipments are housing starts and water heater

lifetimes.

• Water heater retirement functions are triangular in form. Electric water heater lifetimes

range from 6 to 21 years, with a likeliest of 14 years. Natural gas water heater lifetimes

range from 5 to 13 years, with a likeliest of 9 years. We assumed the lifetimes of LPG and

oil water heaters were equal to the lifetime of natural gas water heaters.

• When a water heater is retired, it is always replaced with a water heater of the same fuel

type; therefore, changes in market share for different fuel types are affected only by fuel

choice in new housing. We also assume there is no market for used water heaters.

• The fraction of new housing units with shared water heaters remains constant over time.

• Market share of water heaters to new housing units is affected by three factors: fuel price,

equipment price, and household income.

• Equipment cost elasticities are derived from operating cost elasticities, water heater

lifetime, and fuel-dependent implicit discount rates.

• Household income affects market share via average forecast national household income

(AEO2000) and income elasticities.

• Most water heaters installed in new homes just meet the minimum efficiency levels.

2.8 NATIONAL ENERGY IMPACTS (NES) ANALYSIS

The implementation of a particular standard (or the decision not to implement a standard) will

have direct consequences for future fuel consumption and consumer expenditures. The NES

summarizes these consequences for each trial standard level. The net present value of an option

represents a single figure of merit for evaluation of its desirability. 

The NES predicts the primary energy savings and cost savings of trial standard levels. Total

national energy consumption, as well as costs and savings from proposed water heater standards are

projected to 2030. From this result, net present value and source energy savings are calculated for

each trial standard level. Energy and cost savings predictions serve as input to other impact

assessment analyses (Environmental Analysis, Net National Employment Impacts, Utilities Impacts

Analysis). Assumptions for the NES are:

• The discount rate for calculating societal net present value is 7%.

• Energy savings are based on source consumption. Cost savings use site consumption.

• To calculate a projected marginal energy price for each year, we adjusted the projected

energy price as follows. For each fuel, we calculated the average marginal price for all

households using that fuel for water heating. We divided this by the average price for
a For further explanation about NEMS, please refer to the U.S. Department of Energy, Energy Information

Administration documentation. A useful summary is National Energy Modeling System: An Overview 1998.

DOE/EIA-0581(98), February 1998.

2-9

that fuel for the same households, giving us the ratio of marginal to average price. We

then projected the marginal price in future years by multiplying the projected fuel price

in each of those years by this ratio. 

• Retail prices of water heater units are the average retail price from the LCC analysis.

• Energy price projections are from AEO2000 and GRI2000.

• Electricity source to site conversion factors vary over time — yearly values are from the

AEO2000 forecast.

• Gas source to site conversion factor is assumed to be 0.9.

• Average annual unit energy consumption is calculated from weighted average unit energy

consumption (UEC) of the water heater stock.

 • Average installation costs are average installation costs from the LCC analysis.

2.9 MANUFACTURER IMPACTS ANALYSIS (MIA)

The MIA focuses on financial and non-financial impacts of the trial standard levels on water

heater manufacturers. The financial analysis is based on expected future cash flows. An annual cash

flow analysis is used as a measure of potential investment acceptability by determining a total value

today of the future cash flows, implicitly including the cost of capital. The financial analysis was

conducted using the Government Regulatory Impact Model (GRIM). GRIM used the following

inputs:

• Estimated manufacturer costs and investments from the GAMA data submittal and from

independent consultants’ data;

• Financial information (e.g., tax rate, working capital, depreciation) is obtained from SEC

10-K statements, other publicly available industry statistics (e.g., Robert Morris

Associates), and manufacturer interviews; and

• Future shipments from the Shipments Analysis.

In addition to financial impacts, a wide range of quantitative and qualitative effects may occur

following adoption of a standard that may require major changes to water heater manufacturing

practices. Many of these qualitative effects were identified through interviews with the water heater

manufacturers.

2.10 UTILITY IMPACTS ANALYSIS 

The effects of proposed water heater energy-efficiency standards on the electricity and gas

industries are analyzed using a variant of U.S. DOE/EIA’s NEMS,a

 called NEMS-BRS, which stands

for National Energy Modeling System–Building Research and Standards. The analysis presents the

impacts of standards on utilities by reporting several key industry parameters, notably energy sales,
2-10

electricity generation, and electrical generation capacity. Analysis of the effects of standards on the

natural gas sector includes reports of residential consumption of natural gas and the change in natural

gas used to generate electricity. The energy savings associated with each proposed trial standard level

from the NES model become input into NEMS-BRS. We show results from the reference case as well

as scenarios for high and low economic growth.

The utility analysis uses the assumptions of the AEO2000 and treats water heater efficiency

standards as variations in policy. Because none of the trial standard levels reduces demand by more

than 1% of total U.S. electricity generation and gas consumption in any given year, its effect cannot

be detected directly by NEMS-BRS. Therefore, simulation runs are done for larger reductions in

demand and results are interpolated between the AEO2000 reference case and these runs. We

assumed that the measured effects are linear.

2.11 ENVIRONMENTAL ANALYSIS

The environmental analysis uses NEMS-BRS to provide information about the effect that new

water heater standards would have on the quantity of pollutants and other emissions. For each trial

standard level, total power sector carbon and NOx emissions and estimated household emissions for

carbon, NOx, and SO2 are reported. The outcome of the analysis for each trial standard level is

reported as a variation from the AEO2000 results. The assumptions and inputs to the analysis are

similar to the utility analysis.

2.12 NET NATIONAL EMPLOYMENT ANALYSIS

Net national employment impacts from water heater standards are defined as net jobs created

or lost in the general economy as a consequence of five factors: (1) reduced spending by end-users

on energy (electricity, natural gas, LPG, and oil); (2) reduced spending on new equipment by the

energy companies; (3) increased spending on new water heaters; (4) increased spending on the

installation of new water heaters; and (5) the associated indirect effects of those four factors

throughout the national economy.

To develop these results, an input/output model (ImBuild) of the U.S. economy was used to

estimate the effects on different major sectors of the U.S. economy most relevant to buildings and

their net impact on employment.7, 8 The model was developed by Pacific Northwest National

Laboratory to estimate the employment and income effects of building energy technologies and is

itself a special-purpose version of the Impact Analysis for Planning (IMPLAN), a national inputoutput model, originally developed by the U.S. Forest Service in cooperation with the Federal

Emergency Management Agency and the Bureau of Land Management. The IMPLAN model was

developed by the Minnesota IMPLAN Group.9

An input/output model analyzes the interrelationships within an economy among businesses,

and between businesses and consumers (including government entities), and captures all monetary

market transactions for consumption for a given time period. These interrelationships between the

various sectors of the economy are summarized as mathematical formulas and allow one to analyze
2-11

the effects of a change in one or more economic activities on an entire economy (e.g., changes in

investment, monetary or tax policy).

 In comparison with simple economic multiplier approaches, ImBuild allows for more

complete and automated analysis of the economic impacts of energy-efficiency standards in buildings.

The model takes user-supplied inputs to estimate employment effects at the national level. It uses a

35-sector model of the national economy to model the economic impacts of residential and

commercial building technologies.

The assumptions made for this analysis are:

• The economy is considered “closed” and 100% of the investment in energy-efficiency

technology has an opportunity cost in the U.S. economy’s current activity. Funds

necessary to finance investment are drawn proportionately from all sectors of the economy

(i.e., personal/household consumption represents 70% of total spending; gross private

fixed investment, 10%; federal defense spending, 2%; federal non-defense spending, 6%;

and state and local government spending, 12%. These percentages are close to the actual

distribution of final demand among these sectors as noted in M.J. Scott7).

• 100% of the capital cost premium associated with the new energy efficiency technology

is purchased directly from the Household Appliances sector of the model.

• Cost savings to end users and saved utility investment funds are recycled back into the

economy.
2-12

REFERENCES

1. U.S. Department of Energy-Office of Energy Efficiency and Renewable Energy, Procedures,

Interpretations and Policies for Consideration of New or Revised Energy Conservation

Standards for Consumer Products; Final Rule. Federal Register, 1996. 61(136): p. 36974-

36987

2. U.S. Department of Energy - Energy Information Administration, Annual Energy Outlook

2000: With Projections Through 2020, December, 1999. Washington, DC. Report No.

DOE/EIA-0383(2000). <http://www.eia.doe.gov/oiaf/aeo/>

3. U.S. Department of Energy - Energy Information Administration, Residential Energy

Consumption Survey: Household Energy Consumption and Expenditures 1997,1999.

<http://www.eia.doe.gov/emeu/recs/recs97/publicusefiles.html>

4. U.S. Department of Energy-Office of Codes and Standards, Marginal Energy Prices

Report,1999. <http://www.eren.doe.gov/buildings/codes_standards/applbrf/pdfs/

marginal_energy_price.pdf>

5. Chaitkin, S., J. E. McMahon, C. D. Whitehead, R. V. Buskirk, and J. Lutz, Estimating

Marginal Residential Energy Prices in the Analysis of Proposed Appliance Energy Efficiency

Standards. In ACEEE 2000 Summer Study on Energy Efficiency in Buildings. 2000. Asilimar,

CA: American Council for an Energy-Efficient Economy. 9: p. 25-36. 

6. Gas Research Institute, 2000 Edition of the GRI Baseline Projection of U.S. Energy Supply

and Demand to 2015, 2000. Arlington, VA. Report No. GRI-00/0002.1. 

7. Scott, M. J., D. J. Hostick, and D. B. Belzer, ImBuild: Impact of Building Energy Efficiency

Programs, April, 1998, Pacific Northwest National Laboratory. Richland, WA. Prepared for

the U.S. Department of Energy under Contract DE-AC06-76RLO 1830. Report No. PNNL11884. 

8. Scott, M. J., D. J. Hostick, D. B. Elliott, and R. W. Schulz, Impact of Building Technology,

State and Community Programs on United States Employment and Wage Income, April, 1998,

Pacific Northwest National Laboratory. Richland, WA. Report No. PNNL-11843. 

9. Minnesota IMPLAN Group Inc, IMPLAN Professional: Social Accounting and Impact

Analysis Software, 1997. Stillwater, Minnesota.