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7 THE TREASURY DEPRECIATION MODEL 

Geraldine Gerardi, Hudson Milner, Leslie Whitaker, 

and Roy Wyscarver 

I. INTRODUCI10N 

Depreciation refonn was a controversial issue during the tax refonn debate 

with numerous depreciation systems proposed. The debate over depreciation 

concentrated primarily on the proper balance between lower statutory rates and 

greater depreciation allowances, and secondarily on improvements in the measurement of income through both more realistic measures of depreciation and 

adjustments for inflation. The principal model the Office of Tax Analysis 

used to evaluate the revenue consequences of depreciation proposals was the 

Treasury Depreciation Model. 

For any proposed tax system the depreciation model calculates depreciation 

deductions based on investment estimates by type of asset within a set of 

industries. These estimates enable the model to operate between the micro 

level of the finn, where investment is difficult to forecast, and the macro 

level, where detail is inadequate to evaluate alternative tax proposals. The 

investment estimates are derived primarily from data on investment by industry 

and type of asset for 1970 through 1985 from the Bureau of Economic Analysis 

(BEA). The BEA data are modified for use in the depreciation model to exclude 

investment that is not eligible for depreciation, to extrapolate investment to 

1992, to allocate investment to depreciation categories, and to allocate 

investment to the corporate and non-corporate sectors. The model currently 

considers 72 assets in 55 industries. 

Although these investment estimates provide the basic data to the model, 

they must be supplemented by other data to calculate changes in deductions and 

tax revenues. For example, tax return data from the IRS Statistics of Income 

are used to estimate the amount of investment depreciated by each depreciation 

method and the amount of tentative depreciation and investment credit changes 

carried back or forward as a result of inadequate taxable income. 

The authors wouJd like to express their appreciation to Donna Harrell for preparation of the 

manuscript and tables. 

203 
204 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

To compute total changes in calendar year tax liabilities as a result of 

alternative depreciation proposals, the model calculates the change in depreciation claimed in the current year by adding to the tentative current change 

the carryforward deductions from prior years, subtracting the amounts not 

usable in the current year and adding the amounts carried back to prior years. 

Calendar year tax liabilities are then computed by multiplying the change in 

deductions for the year by each sector's effective tax rate (calculated from 

both statutory tax rates and simulations of the Treasury's corporate tax 

model) to determine the relationship between depreciation deductions and 

taxable income. The depreciation model also computes the investment tax 

credit (lTC) claimed for each year in the simulation period, including the 

interaction of depreciation deductions and lTC carrybacks and carryforwards. 

The depreciation model was used to estimate the revenue effect of the 

changes in the lTC and depreciation provisions under the Tax Reform Act of 

1986. The Act generally repealed the lTC for equipment. which under prior law 

generally was 10 percent of qualified investment. In addition to repealing 

the lTC. the Act reduced the amount of tax credits that could be carried over 

to future years. The Act changed the provisions governing depreciation allowances by replacing the six recovery period classes under prior law with eight 

classes-six for personal property and two for real estate. The Act also 

modified expensing provisions. 

Based on the Administration's August 1986 investment forecast, the mod~l 

shows that the changes in the lTC and depreciation would increase calendar 

year tax liabilities by approximately $256 billion through 1992. After 

certain "off model" adjustments, the estimates were approximately $260 billion 

over this calendar year period and about $23 I billion over the fiscal year 

period ending with fiscal year 1992. 

The results described in this paper illustrate one use of the depreciation 

model-estimating the revenue effect of a change in the tax law over a certain 

period of years. The model is also used to devise depreciation proposals with 

a targeted revenue cost, which may then be evaluated for their reduction in 

the cost of capital (see Chapter 5). Alternatively. a proposal that meets a 

given cost of capital objective can be evaluated for its revenue consequences. 

Finally, a joint goal for the cost of capital and revenue cost could be 

specified and depreciation proposals devised to achieve that goal. 

The remainder of this paper is organized as follows. Section II describes 

the changes in the investment tax credit and depreciation provisions under the 

Tax Reform Act of 1986. Section III continues with a description of the data 

used by the depreciation modeling system: section IV addresses the actual 

model in some detail. Finally. section V presents the model's estimated 

revenue effects from simulating the tax reform changes in depreciation allowances and investment tax credits and discusses the results. 

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The Treasury Depreciation Model 205 

II. A DESCRIPTION OF lTC AND DEPRECIATION CHANGES 

This section describes the changes in the investment credit and depreciation provisions under the Tax Reform Act of 1986 that were evaluated in part 

by the use of the depreciation model. Each change is discussed in the order 

it was evaluated by the model: (l) repeal of the lTC for equipment; (2) reduction of carryforwards of investment tax credits; (3) changes in expensing; and 

(4) changes in the depreciation provisions. 

Prior to the Tax Reform Act a 10 percent lTC was generally allowed for 

investment in new equipment (and used equipment up to $125,000). Short-lived 

equipment in the 3 year Accelerated Cost Recovery System (ACRS) depreciation 

class was permitted a 6 percent credit. Assets that took more than one year 

to construct could receive credits on qualified progress expenditures (QPE's) 

made during the period of construction before the asset was completed and 

placed in service. After 1982 the basis against which depreciation allowances 

were permitted was adjusted down by one-half of the investment credit earned 

unless the credit percentage was reduced by two percentage points. Investment 

in buildings was not allowed an investment credit. 

The Tax Reform Act of 1 986 abolished the lTC after December 3 1 , 1985. 

unless transition rules apply. Some property will continue to receive the 

investment credit for various periods through 1 990 depending upon the asset 

depreciation range (ADR) life of the asset, provided it satisfies certain 

binding contract criteria or was specifically identified in the Act as transition property. The depreciable basis of assets that qualify for transition 

treatment are reduced by the full amount of the credit and continue to use 

pre-reform depreciation schedules. 

Accompanying repeal of the investment credit is the elimination of basis 

adjustments to depreciable assets associated with investment credits and the 

reduction of carryforwards of investment credits. Under prior law, investment 

credits not usable in the current year because of inadequate tax liability 

were carried back 3 years and forward 15 years. Under the Tax Reform Act, tax 

credits carried forward from prior years and newly earned credits are allowed 

in full for 1986, but are reduced by 17.5 percent in 1987 and by 35 percent 

after 1987. 

The Tax Reform Act also changed expensing provisions. Under prior law 

$5,000 of investment could be directly expensed (i.e., deducted in full) in 

1986. This amount was scheduled to increase to $7,500 in 1988 and to $10,000 

in 1990 and thereafter. The new law expands the amount eligible for expensing 

to $10,000 in 1987. subject to certain restrictions. The restrictions generally limit the amount expensed to taxable income derived from any trade or 

business. Thus, expensing deductions cannot be used to offset income from 

other sources. Also. the $10.000 deduction is reduced dollar for dollar as 

the amount of annual investment exceeds $200.000. 
206 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

The Tax Reform Act also replaced the prior ACRS depreciation system with a 

new depreciation system. The prior ACRS system depreciated assets over 3, 5, 

10. 15 and 19 years. Assets in 3, 5. 10 and 15 year classes were depreciated 

by a method similar to 1 SO percent declining balance (DB) with an switch to 

straight line to maximize depreciation allowances. Low-income housing and 

assets in the 19 year class were depreciated at 200 percent and 175 percent 

DB. respectively, with a switch to the straight-line method to maximize the 

present value of depreciation deductions. 

The new depreciation system uses 200 percent DB for assets in the 3, 5. 7 

and 10 year classes and 150 percent DB for assets in the 15 and 20 year 

classes with an optimum switch to straight line to maximize depreciation 

allowances. Real estate is depreciated using the straight-line method over 

2 7. 5 years for residential real estate and over 31.5 years for other real 

estate. The new system applies in I 987, but is optional for assets placed in 

service between July 31 and the end of 1986. The ADR midpoint life primarily 

determines the assignment of property to a class as follows: 

New Ufe 

3 

5 

7 

10 

15 

20 

For ADR Uves 

4 or less 

4.5 to 9.5 

10 to 15.5 

16 to 19.5 

20 to 24.5 

25 or more 

However, certain equipment is treated differently. Autos and light trucks. 

research and experimentation property, and certain technological property are 

placed in the 5 year class. Other assets are assigned new ADR lives by 

statute. Assets without ADR midpoint lives are treated as 12 year ADR midpoint life assets. The Appendix contains a more detailed comparison of prereform and reform depreciation systems according to ADR midpoint life and 

asset type or industry where applicable. 

The Tax Reform Act of 1986 provides an alternative depreciation system for 

property used predominantly outside the United States, for determining the 

proportion of property financed by tax-exempt bonds, and for computing earnings and profits and depreciation for minimum tax purposes. The alternative 

depreciation system uses the ADR midpoint life and is 40 years for structures 

and 27.5 years for low-income housing financed with tax-exempt bonds and the 

straight -line method (except for purposes of the minimum tax). The minimum 

tax allows the 150 percent declining balance method switching to the straightline method for property other than real property. which continues to use the 

straight-line method. 

Under prior law several alternative tax systems applied. The minimum tax 

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The Treasury Depreciation Model 207 

did not apply to depreciation on ACRS personal property. However, for real 

property straight-line depreciati.on was required for minimum tax purposes over 

the applicable ACRS life of 15, 18 or 19 years. Leased property was required 

to use the straight-line method over the somewhat longer tax lives of S , 8, IS 

and 22 years for personal property and 40 years for real property except low 

income housing which used 18 years. Property placed in service abroad was 

able to use the double declining balance depreciation method with an optimum 

switch to the straight-line method over the ADR midpoint life for equipment. 

Real property placed in service abroad was limited to 150 percent declining 

balance with a switch to straight line over 35 years. For computing earnings 

and profits the straight-line method applied to the longer tax lives of 5, 12, 

25 and 35 years for equipment and 40 years for real property. 

Ul. A DESCRIPTION OF THE DATA 

This section discusses the data inputs for the depreciation model. The 

model processes: (a) investment data disaggregated by industry. asset type. 

and asset depreciation range (ADR) and (b) other data which supplements the 

investment data to enable calculation of revenue effects. 

A. The Investment Data File 

The investment data file is the basic data for the depreciation model. The 

Office of Tax Analysis (OT A) created this file from investment data supplied 

by Bureau of Economic Analysis (BEA). This process consisted of four steps: 

(a) adjusting the investment data to investment allowed tax depreciation. (b) 

extrapolating the data through 1992. (c) mapping the BEA industries and asset 

classes into OTA industries and asset classes, and (d) splitting the data file 

into a corporate and non-corporate sector. The subsections below provide 

background about the BEA data file and describe each step of the process used 

to create the investment data file. A detailed discussion of BEA's estimation 

procedure is contained in Gorman, et.al. ( 1985). 

B. The BEA Data 

The BEA investment estimates by industry were obtained from three major 

sources. The first data source, BEA 's plant and equipment expenditure survey. 

provides annual data on investment in nonresidential capital by nonfarm industries. These data are classified on a company basis and provide a two-way 

split by type of asset: total equipment and total structures. The second 

source of information is on investment in structures and durable equipment by 

sector (mining. construction. manufacturing. etc.). which is collected by the 

Census Bureau. These data are available every five years. The third source of 

data is the capital flow tables prepared by BEA from input-output tables for 
208 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

1963, 1967, and 1972, which provide distributions of investment by asset for 

each industry. In those instances where data were nonexistent, adjustments 

were made using interpolation and extrapolation procedures calibrated to 

established benchmarks. 

The investment flows were derived for investment in new capital by type of 

asset for each industry and for transfers of used assets between private 

business and other types of owners. The flows for each industry for investment in new and used assets were distributed by legal form of organization. 

The BEA data provides estimates of investment by industry and by type of 

asset for 1970 through 1985. For years following 1985, investment was calculated from detailed industry growth rates obtained from long-term forecasts by 

Data Resources, Inc. (DRI). 

C. The Data Adjustment Process 

In order to use the BEA data to compute tax depreciation, several adjustments were required. In order to concentrate on depreciation deductions of 

taxable firms, all tax-exempt co-operatives were removed (rural electric 

power, telephone and wholesale trade). Similarly, all investments of nonprofit institutions were removed from the real estate industry. (BEA classified these investments in the real estate industry in order to maintain 

consistency with the National Income and Product Accounts, NIPA). Non~ 

depreciable oil wells, gas wells, and mine shafts were removed from their 

corresponding industries. The assets of Federal Reserve Banks are also 

removed since they do not pay income tax. 

A time series for used investment was created using basic scrap equations 

found in Winfrey ( 1935). Adjustments were made for replacement railroad 

tracks and major structural improvements. Special purpose agriculture structures. railroad tank cars. public utilities, coal fired burners, and other 

asset types were also adjusted to achieve benchmark targets. 

These adjustments to the BEA data produced the basic data for the 

depreciation model. 

D. Extrapolation 

The BEA data file provides data for the years 1970 through 1985. Since the 

depreciation model must simulate proposals for 1981 through 1992, the years 

beyond 1985 were extrapolated in two steps: (a) investment was grown from 

19.86 through 1992 based on estimated growth rates for each industry from DRI. 

and (b) the data was subsequently scaled to conform with the Administration's 

forecast for gross private domestic investment in producers durable equipment. 

residential structures. and non-residential structures. This extrapolation 

procedure provides a consistent basic data set that covers the years for which 

revenue estimates are calculated. 

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The Treasury Depreciation Model 209 

E. Mapping 

Mapping of industries and asset classifications is required because BEA 

industries and asset classifications are not the same as those used by OT A. 

Since BEA uses more detailed industries than OTA, the 61 BEA industries were 

mapped into 55 industry classifications used by OTA. ADR mapping also is 

necessary because not all of the investment attributed to each of BEA 's 65 

asset types corresponds to one and only one ADR classification. Consequently, 

the investment in certain asset types are allocated among several different 

ADR classes depending on the asset type and industry. Investment in other 

asset types are allocable to one and only one ADR class. 

F. The Corporate/Individual Split 

The investment data file was split into two separate data fLles, for the 

corporate and individual (non-corporate) sectors, so that revenue estimates 

could be calculated for each sector. The investment data file was split by 

computing the percentage of total investment by industry that is non-corporate 

and applying that percentage to the investment in each asset within the industry. This percentage is the weighted sum of the percentage of non-corporate 

investment in equipment and structures obtained from statistics of income 

data. 

G. Other Data Inputs 

Although the adjusted investment data file provides the basic infonnation 

needed for the computation of tax depreciation, it is incomplete and must be 

supplemented by data from other sources. For example, it does not contain the 

amount of investment that received straight line depreciation or sum of the 

years digits, or the amount of depreciation deductions claimed for the current 

year or deductions carried forward to future years. The corporate tax model 

with published corporate statistics of income (SOl) data was used . either to 

extract, or where necessary, generate the additional data in a fonn that could 

be used with the investment data. These data include: 

o Percent of corporate and non-corporate investment qualifying for bonus 

depreciation by industry. These amounts are used to determine the 

amount of corporate and non-corporate investment that is expensed, 

respectively. 

o Growth factors to inflate or deflate expensing and bonus depreciation. 

These data are used to estimate real growth in the number of businesses 

by industry and year. 

o Depreciation deductions on structures "in place" as of 1981 estimated 

through 1992 for each industry. These amounts are added to new depreciation to yield total depreciation. 
210 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

o Depreciation deductions on equipment "in place" as of 1981 estimated 

through 1992 for each industry. These amounts are added to new depreciation to yield total depreciation. 

o Interpolation parameters (by percent change in depreciation) by industry for the a) effective tax rate; b) percentage of depreciation 

deductions in net operating losses (NOL); and c) ratio of tentative lTC 

to claimed lTC. 

o Percentage of carryback and carryforward that apply to the ITC computations. 

o Percentage of NOLs carried back and forward that apply to the depreciation computations. 

These additional data complete the input data used in the current version 

of the depreciation model. 

IV. A DESCRIPTION OF THE SIMULATION MODEL 

This section summarizes the operation of the depreciation model program. 

The fll'st subsection highlights the functional operation of the model. A 

subsection follows that provides a more detailed explanation of selected 

computations. The last subsection illustrates how the depreciation model is . 

used with other modeling systems to expand the capabilities of those systems. 

A. The Simulation Process 

The data for each asset in each industry is processed for each year in the 

simulation for present law (Plan X) and proposed law (Plan Y). For each plan. 

the model computes by year an investment tax credit and depreciation deductions by proceeding through the following steps: 

o The asset tax classification is determined. 

o Transition rules are applied. if applicable. 

o Expensing is computed and. if appropriate, the expensed amount is 

subtracted from the cost of property to obtain the adjusted basis. 

o The allowable investment tax credit is computed and. if appropriate, 

the adjusted basis is modified again. 0 Regular depreciation deductions are computed for investment that does 

not receive straight line. 

o Straight-line depreciation deductions are computed for investment that 

is eligible for and chooses to use straight Jine. 

The results are summed for each industry across all asset classifications 

to obtain total investment. total depreciation. and total "tentative" investment tax credit for the industry by year. 

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The Treasury Depreciation Model 211 

Next, the difference between present law and proposed law depreciation 

deductions and lTC and the corresponding difference in calendar year tax 

liabilities and fiscaJ year receipts are computed. (These computations are 

described in greater detail later in the subsection on credit computations.) 

The industry results are available for the corporate sector, non-corporate 

sector, and both sectors combined. 

B. Explanations of Selected Computations 

This section provides detailed explanations of the model's computations for 

expensing. qualified progress expenditures, tax liability, and tax credits. 

J • Expensing 

A finn can elect to deduct the cost of property up to some maximum in the 

year the property is placed into service in lieu of recovering the cost under 

the depreciation rules currently in effect. Only personal property is eligible for expensing. Because the investment data was collected by industry and 

expensing rules apply to the firm, a procedure was developed to estimate expensing on a industry basis for both the corporate and non-corporate sectors. 

Corporate tax model simulations were perfonned to determine, by industry, 

the percentage of cumulative investment less than or equal to expensing limits 

in $5,000 increments up to $50,000. Similar simulations were also performed 

using the sole proprietorship file to obtain percentages for the non-corporate 

sector. These percentages, applied to the investment across an industry in a 

given sector for a specific expensing limit. yield an estimate of expensing. 

Based on the results of regressions, allowances were made to expensing for the 

growth in the number of business over time. 

2. Qualified Progress Expenditures 

Qualified progress expenditures (QPE) are calculated so that their associated lTC can be computed. By looking ahead in the time series. the amount of 

investment that will be put in place in the future is distributed backwards 

through time (the construction period) according to an industry-specific 

pattern. The industries that are affected by qualified progress expenditures 

rules are chemical and petroleum refining equipment, coal and non-nuclear 

power plants, and nuclear power plants. 

Table 7.1 provides an example of this estimation method for QPEs for 

chemical and refining equipment. It is assumed that QPEs in the current year 

are 34 percent of total investment and that this amount was actually spent 

over the prior 4 years of the construction period. The pattern of this distribution assumes that 7 percent of the cost occurred one year ago. 20 percent 

two years ago, 48 percent three years ago. and 25 percent in the first year of 

the construction (four years ago). Once these computations hav.e been completed. the qualified progress expenditures for each year of the simulation 
212 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

Table 7. I Assumptions Underlying Qualified Progress Expenditures 

Number Chemical Coal and Nuclear 

of Years Refining Non-Nuclear Power 

Past Equipment • • b Power Plants Plants 

Construction period 4 .00 7.00 1 I .00 

Total QPE as a percent of 

current year investment 34.00 30.28 30.28 

I 7.00 4.00 16.00 

2 20.00 14.00 14.00 

3 48.00 33.00 12.00 

4 25.00 34.00 12.00 

5 11 .00 I I .00 

6 3.00 11 .00 

7 1.00 12 .00 

8 6 .00 

9 4 .00 

10 1.00 

II 1.00 

•coNCEPT-S. Oak Ridge National Laboratories. Phase VI Update (1983) Report for the 

Energy Economic Data Base Program. EEDB-VI. September. 1984. 

bBased on Energy Information Form 254 and Federal Energy Regulatory Commission 

Form I. The data are based on a specific 1120 megawatt pressurized-water reactor unit that 

is considered to be representative of nuclear units. 

are summed so that the series wiU be available for the computation of the 

investment tax credit. 

The same procedure is applied to the other eligible industries. Since the 

construction period for nuclear power plants is 11 years, the computations 

cover the period 1971 (1982. when QPE rules were enacted, minus II years) to 

2006 (1995, the last year the model estimates, plus II years). In years where 

no actual investment data exists. data was generated by assuming that investment continues to grow at the same rate exhibited by the last two periods of 

actual data. 

3. Tax Computations 

For each industry the depreciation model computes the following changes for 

each year in the simulation: 

0 Tentative total depreciation. 

o Tentat.ive current year depreciation. 0 Tentative deductions carried back. 

o Tentative deductions carried forward . 

o Claimed total depreciation. 

o Claimed current year depreciation and deductions carried back, 

o Claimed deductions carried forward. 

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The Treasury Depreciation Model 213 

o Outstanding carryforward (NOL). 

o Calendar year tax liability, and 

o Fiscal year receipts. 

To compute these changes. summations are required for total depreciation 

deductions under present law (Plan X) and under proposed law (Plan Y). The 

tax calculator begins by computing the tentative change in depreciation as the 

difference between Plan Y and Plan X depreciation deductions. In-place depreciation for equipment and structures is added to present law depreciation to 

yield total present law depreciation. 

Next, the model computes the percentage change in depreciation deductions 

with respect to total present law depreciation. Both the percentage change in 

depreciation deductions and industry classification are used to determine 

three exogenous tax parameters: (a) the effective corporate tax rate for 

depreciation deductions. (b) the percent of total depreciation deductions in 

NOL.s, and (c) the ratio of claimed lTC to tentative lTC (used in the computation of tax credits). These tax parameters are used to calculate the change 

in current year depreciation deductions and to allocate the total depreciation 

change between current year deductions and additions to carryback and carryforward deductions. Tentative changes are computed in four steps. 

First, the tentative change in current year taxable income is computed by 

multiplying the total change in depreciation deductions by one minus the percent of total depreciation deductions in NOLs. Second. the tentative change 

in carryback deductions is computed by multiplying the tentative change in 

N 0 Ls by the percentage of N 0 Ls carried back (obtained from data extracted from 

the corporate SOl). Third, the tentative change in carryforward deductions is 

a residual obtained by subtracting the tentative change in carryback deductions from the tentative change in NOLs. 

The change in current year taxable income is computed as the sum of the 

tentative change due to current year depreciation deductions, the tentative 

change in carryback deductions, and the claimed change in carryforwards from 

prior years (accumulated during prior years of the simulation). For each year 

remaining in the simulation, the claimed change in carryforward deductions is 

computed by multiplying the tentative change in NOLs by the percentage ofNOLs 

carried forward. These carryforwards are accumulated for each year remaining 

in the simulation so that claimed carryforwards will already be computed when 

the simulation reaches a future year. 

Calendar year tax liabilities are computed by sector because effective tax 

rates differ by sector. The effective corporate tax rates are adjusted for 

the rate reductions enacted in the Tax Refonn Act of 1986 by simple proportional adjustment. Thus, the corporate tax rate (derived from corporate tax 

model simulations) is multiplied by (0.40/0.46) for 1987 and by (0.34/0.46) 

for 1988 and the years that follow. The individual tax rates are computed as 

a base rate adjusted to reflect bracket creep that existed prior to indexing 

enacted under the Deficit Reduction Act. In addition, the individual tax 
214 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

rates were adjusted further to capture the rate reductions enacted by the 

Economic Recovery Tax Act. Changes in tax liabilities are then computed by 

multiplying the change in deductions claimed by the effective tax rate for the 

appropriate sector. 

4. Credit Computations 

Following the tax computations. the depreciation model computes the lTC for 

each year in the simulation. The model computes the following changes: 

o Tentative total lTC, 

o Tentative current year lTC, 

o Tentative lTC carried back, 

o Tentative lTC carried forward. 

o Claimed total lTC, 

o Claimed current year and carryback lTC, 

o Claimed ITC carried forward , 

o Outstanding carryforward. 

o Calendar year tax liability. and 

o Fiscal year receipts. 

The procedure for these calculations is similar to that for the tax 

computations for changes in depreciation. Consequently. it will not be 

discussed further here except to note two differences. First, the allocation 

of tentative total lTC to carryforward and carryback credits is more complicated than the same computation for depreciation deductions because the model 

must account for the fact that a change in gross tax will change lTC carried 

back or forward. In other words, if the lTC does not change between present 

and proposed law but depreciation deductions do change, then more or less lTC 

will be carried back or forward . Second. the tax liability computation is 

different because ITCs are applied directly against tax. 

C. Relationship to Other Models 

I . Corporate Model 

The depreciation model is used to supply three categories of data to assist 

simulations made with the corporate model: (a) estimates that adjust depreciation deductions by industry on the corporate SOl file. (b) computations of 

preference amounts that are allocated to corporate returns for computing the 

alternative minimum tax. and (c) estimates that are used to construct an earnings and profit (E&P> net depreciation adjustment for 1990 and beyond. 

For the regular tax. depreciation in the corporate tax model is recomputed 

by multiplying the base year depreciation by an adjustment ratio. This 

ratio is the target depreciation. as estimated by the depreciation model. 

divided by the total base year depreciation on the corporate data base. 

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The Treasury Depreciation Model 215 

For the alternative minimum tax under the Tax Refonn Act (TRA), two 

simulations using the depreciation model are required to produce the appropriate estimates. The first simulation yields depreci~tion claimed under the 

TRA for assets put in place after the law becomes effective; the second simulation produces the minimum depreciation generated by these assets. 

The adjustment for earnings and profit depreciation requires a series of 

depreciation model simulations to capture the nuances of the interactions of 

book income and taxable income within the depreciation system. 

2. Supplemental Model 

The results of the depreciation model are adjusted using a supplemental 

model to take into account changes in the tax treatment of research and development property. The adjustment provided by this model is described in detail 

in section V.B. 

V. RESULTS OF SIMULATING THE EFFECTS OF TAX REFORM 

This section discusses one use of the depreciation model: detennining the 

revenue effects of changes in depreciation allowances and investment tax 

credits in the Tax Refonn Act of 1986. 

A. Simulation Results 

The depreciation model evaluated refonn proposals in the following order: 

repeal of the investment tax credit, reduction in existing investment credits, 

changes in expensing. and changes in depreciation. The order of consideration 

affects the revenue estimate for a particular provision. For example, the 

revenue estimate for changes in expensing is different if it is considered 

before rather than after depreciation provisions. The "stacking order" 

followed for the Tax Refonn Act estimates was statutory tax rate reduction 

frrst, followed by investment credit repeal, reduction in existing credits. 

increase in expensing, and depreciation changes. Stacking order issues are 

discussed in Nester "Interpreting Revenue Estimates: Macro-Static MicroDynamic" in Chapter I of this volume. The effect of general rate reduction, 

which is considered before depreciation and investment credit provisions for 

revenue estimating purposes. is not discussed here. In addition. the effect 

of other provisions which were stacked later. such as the minimum tax, are not 

described here. 

l. Summary 

The revenue estimates produced by the depreciation model after adjustments 

are summarized in Table 7.2. The tax refonn changes in the lTC and depreciation increase calender year tax liabilities by $260 billion through 
2 J 6 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

Table 7.2 Revenue Changes From The Capital Cost Recovery Provisions 

in The Tax Reform Act of 1986, 1986- 1992. 

1986 1987 1988 1989 1990 1991 1992 1986-1992 

($ Millions) 

Individual 3,320 3,1102 5.332 6,729 9,0110 11 .807 13,138 53,208 

Corporate 10.533 15,069 22.408 29,452 36.880 254 46,3511 206.954 

Total 13,853 18 ,1170 27 .741 36.1111 45.961 SII.062 S9.496 260,163 

*These estimates may differ from other published estimates, because they are based on a 

different economic forecast and include only selected capital cost recovery provisions. 

calendar 1992. Calendar year liabilities increase from $13.9 billion in 1986 

to $59.5 billion in 1992 as transition provisions phase out, the economy 

grows, and a larger fraction of investment becomes eligible for the new 

depreciation schedules. 

The change considered first, investment credit repeal, provides revenue 

increases roughly proportional to investment in equipment. The changes considered second and third, the reduction in existing credits and increases in 

expensing. have relatively small effects concentrated in the early years. 

Depreciation provisions. which were considered last, first reduce and then 

increase revenue after a few years as the revenue increase from the less rapid 

depreciation schedules for structures overtakes the revenue loss from the more 

rapid depreciation schedules for equi.pment. 

Results of the depreciation model are adjusted to produce the final set of 

revenue estimates. These adjustments take into account current data for the 

35 percent cutback of ITCs, the elective 15 year carryback for certain taxpayers, the treatment of R&D property. and recapture provisions for auto and 

truck leasing. These adjustments are necessary to produce a fmal set of 

revenue estimates for the tax reform proposals. Several adjustments made 

using the supplemental model are described in section B. 

2. Investment Credit Repeal 

The first change evaluated by the model is repeal of the investment tax 

credit. Tentative investment credits before reform are calculated according 

to the classification of the asset. Three-year property receives a 6 percent 

investment credit and longer lived personal property receives a lO percent 

credit unless the property is expensed. 

The translation of tentative credit changes to actual tax changes requires 

adjustments for the interaction of credits with depreciation and adjustments 

for restrictions on the use of credits and deductions. The computation of 

revenue changes associated with repeal of the investment credit is described 

in more detail below. 

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The Treasury Depreciation Model 217 

The baseline investment series for 3. 5, 10, and 15 year personal property 

eligible for the credit under prior law for calendar years 1986 through 1992 

is shown on Table 7.3. Within each asset class the amount of investment is 

shown that is adjusted in basis for investment credits, is expensed, is 

allowed ACRS depreciation, and selects straight-line depreciation. Investment 

expenditures fall primarily in the 5 and 19 year classes. For 1986, $284 

billion or 49 percent of investment was accounted for by 5 year equipment. 

Buildings, which received a 19 year depreciation period, accounted for $153 

billion or 27 percent of total investment. Based on the estimates of investment shown on Table 7.3, the model calculates tentative depreciation deductions before repeal of the investment credit. These estimates for calendar 

years 1986 through 1992 are shown on Table 7.4. 

Table 7.5 summarizes the computation of actual tax changes from repeal of 

the investment credit and shows the total change in calender year liabilities 

and fiscal year receipts. These totals include various interactions between 

credit~. depreciation allowances and the other tax provisions shown on the 

table. After a presentation of total investment for reference in lines 1 to 3 

of Table 7.5 and total tentative depreciation deductions in the base and 

revised cases in lines 4 and 5, respectively. the differences in tentative 

depreciation deductions from repeal of the lTC are presented in line 6. 

Tentative depreciation deductions increase by approXimately $16 billion per 

year by 1992 from the elimination of the basis adjustment. 

Based on simulations of the corporate tax model, the tentative depreciation 

allowance change is divided into three parts: the portion used in the current 

year, the portion carried back to one of the previous three tax years, and the 

portion carried forward to future years. Because some deductions not usable 

against current year tax liability (carrybacks) are assumed to reduce tax liability for a prior year, any pennissible reduction in prior year tax liability 

from the carryback is a reduction in tax liability affecting Federal government revenue for the current year. These current and carryback deductions 

from Jines 7 and 8 are totaled in line II. The third portion of depreciation 

deductions, the position that cannot be used currently or carried back to a 

prior year due to inadequate tax liability. is carried forward to a future 

year. perhaps to be usable later as a carryforward (line 9). 

Line 12 takes into account the stock of net operating loss carryforwards 

that some finns have from the past that are usable in the current year. Thus. 

the current year change shown in line 10 is the sum of current and carryback 

use of currently earned tentative depreciation deductions plus the amount of 

carryforwards from previous years used in the current year. The change in the 

stock of outstanding carryforwards of net operating losses maintained by the 

model is presented in Jjne 13. 

The "bottom line" effect on tax receipts of depreciation related changes 

induced by repeal of the investment credit is presented in line 14 by calendar 

year and in line 15 by fiscal year. The tax rate applicable to depreciation 

allowances is calculated by the model from the basic statutory rates of 40 
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21 8 

Geraldine Gerardi/Hudson Milner/leslie Whitaker/ o~ W~scarver I 

Table 7.3 

Total Investment by ACRS Depreciation O ass I 

Before TRA 86, 1986-1992 

I ACRS Class 1986 1987 1988 1989 1990 1991 1992 

(S Millions) 

3 Year Personal Property 

Buls Adjustment 1,319 1,460 

1.638 1,9211 2,156 2.341 2.546 I 

Expensing 1.606 1,616 2,466 

2,6S2 3.268 3.273 3.288 

Regular 63.187 69.711 78.161 91

,889 102,739 111

,542 121,2S2 I Straight Line 2,292 2,5211 2.83S 3.333 3 ,726 4.046 4,3911 

S Year Personal Property 

I Basis AdjuStment 7.834 8.807 9,934 11.634 13,071 14,353 15,282 

Expensing 6,039 6.187 9,461 10

,144 12

,596 12

,843 13,129 

Rqular 260

,463 292,510 329.779 387

.067 436

,020 480,215 529.839 

Straight Line 

9,447 10

,609 11

.961 14.039 15.814 17,417 19,217 

I 10 'Veer Personal Propeny 

Basis Adjustment 296 328 366 412 4SI 489 207 

E•penslng 10 10 IS 16 19 19 20 

I Regular 11.012 11.801 12.784 14,037 JS, l74 16,352 18.099 

Straight Line 399 428 46S S09 S50 S93 656 

IS Year Penonal Property 

I Basis Adjustment 813 908 1,011 1,160 1,282 1,378 959 

EJtpensing 12 

12 19 20 24 24 2S 

Reautar 27

,426 30,033 33

,240 38,090 42,068 45,238 49.6

17 

Stralaht line 99S 

1,089 1,206 

1,382 

1,526 1,641 

1.800 

I 5 Year Real Property I 

EJtcept Low Income 

Basis Adjustment 9S 0 0 0 0 0 0 I EJtpensing 0 0 0 0 0 0 0 

Regular 

11.967 0 0 0 0 0 0 

Straight Une 8.974 0 0 0 0 0 0 

lS Year Real Propeny 

Low Income I 

Basis Adjustment 0 0 0 0 0 0 0 

E•pensing 0 0 0 0 0 0 0 I Reaular 6.737 7,4113 11 .282 9,015 9 ,701< 10,5112 11.520 

Straiaht Line 237 264 292 318 342 373 406 

19 Yur Real Property 

Basis Adjustment 0 0 0 0 0 0 0 I 

Expensing 0 0 0 0 0 0 0 

Rqular 1111

.335 110,392 122 ,23• 133.177 144,435 157.944 172,574 I Straight Une 64.758 80.633 119.173 97.077 105,453 115.342 126.089 

Total 514,254 636.809 

715,320 817,898 910.419 996.004 

1.090.932 

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Table 7.4 Total Deductions by ACRS Depredation Class 

Before TRA 86, 1986-1992 

ACRS Class 1986 1987 1988 1989 1990 1991 1992 

($ Millions) 

3 Year Personal Propeny 56,162 57.518 62.340 70,327 80,411 89.722 97.899 

S Year Personal Property 242,233 257.821 28S,SS9 315,311 354,163 399,006 447,296 

10 Year Personal Property 5,899 7,077 8,335 9,730 11 .250 12,100 13,144 

IS Year Personal Property 10,146 12,2SS 14S75 17,206 20,200 23.392 26,841 

15 Year Real Property 

E11cept Low lncome 37 ~ 35,259 32,505 30,301 28.679 27,084 25,121 

IS Year Real Properly 

Low Income 2,669 3.222 3,793 4,402 5 ,033 5.699 6,416 

19 Year Real Property 15,614 27,554 40,859 54.700 68.996 83,878 99,617 

Total 370,290 400,706 447 ,966 501,977 568,732 640,881 716,933 

percent in 1987 and 34 percent thereafter with adjustments to these statutory 

tax rates calculated within the model based on the results of simulations of 

the corporate model. Fiscal year receipts are calculated from the calendar 

year figures from a rule of thumb division of calendar year liabilities 

between fiscal years. All amounts are calculated for the corporate and noncorporate sectors separately and aggregated to the totals presented. A 

similar set of calculations is then performed by the model for investment 

credit changes, shown starting on line 16. The difference between baseline 

and tax reform tentative investment credits in lines 16 and 17 is presented in 

line 18 as the tentative change. The portions of the tentative change used in 

the current year or carried back to one of the previous three years shown in 

lines 19 and 20 are summed in line 23. The portion of the outstanding investment credit carried forward from previous years shown in line 24 is added to 

determine the actual change in line 22. The stock of outstanding carryforward 

is adjusted for the difference between past carryforward used or lost and 

current year additions to the carryforward in line 25. Changes in fiscal year 

receipts in line 27 are calculated from calendar year receipts in line 26. 

The total change in line 28 is the sum of depreciation induced changes in 

tax liability in line 14 and investment credit changes in tax liability in 

line 26. Similar sums are calculated for fiscal year receipts in lines 15, 

27. and 29. The total tentative ~evenue change in investment credits through 

t 992 of $337 billion becomes a $230 billion dollar change after carryforwards. 

carrybacks and associated depreciation adjustments. These are the amounts 

associated with repeal of the investment credit before the reduction in 

investment credits that will be discussed next. 

3. Reduction in Investment Credits 

The second set of tax reform changes evaluated by the depreciation model is 

the reduction in investment credits allowed. Investment credits allowed under 
Table 7.5 Summary of the Effects of the Proposal to Repeal the ,~ Investment Tax Credit of TRA 86, 1986-1992* 0 

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198() 1987 1988 1989 1990 1991 1992 !. 

($ Millions) Q. ... Investment ;:) 

I Total .574,254 636,809 71.5.320 817,898 910,419 996,004 1.090.932 n 

2 New 494.894 .5.51.343 618,800 707.067 783.012 849.83.5 924.278 0 

3 Used 79.360 8.5.466 96 • .520 110.831 127.407 146,170 166.6.53 n 

2 Depreciation Q. 

4 Tentative Plan X (ACRS) 370.290 400,706 447.966 501,977 .568.733 640.881 716.933 -· -. s Tentative Plan Y (Re.pea.l) 371.940 404,797 4.54,406 .510.939 .580,.531 6.54.83.5 732.674 ::c 

6 Tenlative Change L.650 4.091 6 ,440 8 .962 11.799 13.9.54 1.5,742 c: 7 Current Year 966 2.466 3.974 .5,624 7,473 8.939 10.144 Q. 

II C11rryb~t k 18.5 439 666 9012 1. 168 1.354 I.Sll ~ 9 Carryforward 499 1,186 1.800 2.437 .1,1.58 3.661 <4 ,086 ;:) 

10 Actual Change 1.1.51 2.939 4 ,7S6 6.763 9 .047 10,91.5 12 • .528 

I I Current Year + C11rryback 1.1.51 2,90.5 4,640 6 • .52.5 8,641 10.293 11,65.5 ~ IZ Carryforv.anl u,aJ 0 34 11.5 239 406 622 873 5" 

13 Ot.ll,tanding Carry1orward (NOLl 499 1.6.51 3.336 .5 . .534 8 ,286 11.32.5 14,538 n 

14 Calender Year Tu Liability -408 -9.57 -1.3.52 -1,872 -2 . .514 -3 .046 -3 • .506 .., 

........ 

IS Fiscal Year ReceiptS -218 -699 · 1, 168 - 1.6<43 · 2.222 · 2.806 -3 .197 fi' 

Investment Tu Credit 

16 Tentative lTC Plan 36.114 40,40.5 4.5,3.53 .52.63.5 .58,873 6<4 . .508 63,368 c;· 

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II! 

Tt:ntatl

Tent11tlve 

ve 

Change 

lTC Plan 

-24

12

.

.

013 

110 

-34

6

.

.

348 

0.57 

-41

3,608 

,746 -.51.313 

1.322 

-51,154 

1,119 

-64.508 

0 

~3.368 

0 ~ ::T 

19 Current Year ·IS. ISS -21 .824 -26.791 ·33,219 -37,486 -42.222 · 41 . 110 --· 20 

21 

C

C.trrytorward 

arryhuck 

-8.41.5 

-443 

-11.898 

·626 - 14,

-

207 

748 

- 17,

-

189 

90.5 

· 19

- 1.013 

.2.5.5 · 21,171 

-1, 114 

· 21

-1.113 

,14.5 ~ n 

22 Actual Change · 1.5 . .598 -24,66.5 -32 • .530 -41.201 -47,874 · 54 . .578 -.5.5.034 .., 

-. 23 Current Year + Carryback - 1.5,.598 -22.4.50 -27,.539 -34.124 -38.499 -43.336 ·42,223 , 

24 Carrytorward Used 0 · 2.21.5 -4,991 -7 .077 ·9.374 · II ,242 · 12.811 0 

2S Outsusnding Carryforward (lTC) -8,41.5 - 18.098 -27,314 -37,426 -47,306 -.57.23.5 ~.5 . .569 

26 Cah:nder Year Tall Liability 14 ,.540 23.021 29.671 36.734 42.694 48,766 48,641 

27 Fistal Year Receipt~ 7 ,937 19.194 26,196 3 ,747 40.0.5.5 46.110 48,484 

Total Change 

2M Calender Year Tax Liability 14,132 22.06<4 28.319 34.862 40.181 4.5.720 4.5, 13.5 

29 Fi-cal Vt!ar ReceirtS 0 26.213 2S.623 32. 103 37.833 43 . .304 4.5.187 

*These estimates may differ from other published estimates because they are based on a different economic forecast. 

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transition rules or carried forward from previous years could be used in full 

in 1986. but were scaled back 17.5 percent for 1987 and 35 percent for 1988 

and thereafter. Marginal revenue changes from this provision are calculated 

by taking the difference between depreciation model runs that add the investment credit cutback provision to the investment credit repeal provision 

discussed above and the depreciation model run for investment credit repeal 

alone. This difference is concentrated in calendar years 1987 through 1990 

when unused credits are their maximum and some investment credits are being 

earned on transition property. 

4. Increase in Expensing 

The Tax Refonn Act of 1986 increases expensing of personal property to 

$10,000 in 1987; under pre-refonn Jaw the increase phases in over a 4 year 

period. The Act also limits the amount eligible to be expensed to taxable 

income derived fonn the active trade or business in which the property is used 

and phases out the ceiling dollar for dollar on taxpayer investment in excess 

of $200,000. The revenue cost of this provision totals about $5 billion as 

shown in Table 7.6. concentrated in the early years when current law allows 

expensing of only $5,000 or $7,500. 

Because limitations on expensing take place at the firm rather than industry level. adjustments to the depreciation model for these changes are based 

on simulations of the corporate tax model to obtain "rules of thumb" cutbacks 

to apply to expensing. 

5. Depreciation Changes 

As described in Section 11, TRA completely changed the tax treatment of 

depreciable assets. The ADR system classified assets by their average useful 

Table 7.6 Revenue Estimates for Expensing Provision Changes in TRA86• 

1987 1988 1989 1990 1.991 1992 1986-1992 

Calendar Year Liability 

Individual -1.16 I -586 -393 -123 5 -48 -2,306 

Corporate -1,386 -641 -487 -148 7 -62 -2 .717 

Total -2.547 - 1.227 -880 -270 12 -110 -5 .023 

Fiscal Year Receipts 

Individual -436 -946 -514 -292 -75 -15 -2.276 

Corporate -831 -939 -549 -283 -55 -35 -2.692 

Total -1.267 - 1.885 -1.062 -575 -130 -49 -4.968 

*These estimates may differ from other published estimates because they are based on a 

different economic forecast. 
222 Ge.raJdine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

life in the hands of the purchaser. Most equipment was classified as 5-year 

ACRS property under pre-reform law. The Tax Reform Act moves this property 

primarily into the 5 and 7 year double declining balance classes. Thus, most 

personal property obtains approximately equal or more rapid depreciation from 

the tax change because 5-year ACRS depreciation is approximately equivalent to 

150 percent declining balance (all with an optimum switch to the straight-line 

method). The depreciation lives of structures are lengthened from 19 to 27.5 

or 31.5 years and their depreciation is reduced from the 175 percent declining 

balance method to straight line. 

The amount of investment in each of the eight new classes is given in Table 

7. 7 for calendar years 1986 through 1992 using the Administration's August 

1986 forecast. The distribution of investment by the new depreciation 

categories is most clearly seen in 1991 and 1992 when transition treatments 

have ended. (Transition property is shown as an aggregate rather than by 

class at the bottom of Table 7. 7.) The largest class is 5 year property. The 

next two largest classes are the real property classes for residential and 

nonresidential building followed by the 7 year personal property class as the 

fourth largest investment category. 

Total deductions for each class by calendar year are presented in Table 

7. 8. These deductions when adjusted and converted to tax changes are compared 

with pre-reform law to obtain the summary of differences in Table 7. 9 for the 

depreciation changes alone. 

Table 7. 9 shows the effect of two factors on revenue changes associated 

with depreciation provisions in the Tax Reform Act. First, the more rapid 

depreciation method for most equipment combined with the large amount of 

investment in the 5 year class produce a revenue loss for 1987 and 1988 as 

well as for 1986 (when the new schedules were optional for the last five 

Table 7.7 Total Investment by TRA 86 Depreciation Class, 1986-1992 

De~reciation Class 1986 1987 1988 1989 1990 1991 1992 

($ MiUions) 

Class I (3 yeerl <40,3SS 13.663 1!1.3119 17.933 20,0<42 21 ,609 23,368 

Class 2 (5 ~ar) 207.128 1<40.31-4 288,!1« 3!13.903 398,487 <436,010 477,113 

Cla~s 3 (7 year) 2.317 86.299 110.717 141 .709 160.903 177.601 196.606 

Class <4 (10 ~ar) ll ,SIIO !1, 1611 6.!163 11.209 9,023 9,829 10.769 

Class 5 (IS year) .56.3!11 22,!121 29.7110 37.020 «.196 6!1.3-40 70.989 

Cla~s 6 (20 year) 4,924 R60 1,020 1,155 1,273 1.376 1.486 

Class 7 (27 .S year) <45.110 67 .252 15,920 K2 .793 1!9.301 97,<494 106.293 

Class 8 (3U year) 0 98.307 124.744 147,032 1611.5!10 1116.7<46 20<4.306 

Transilion 206,<490 102.<425 62.6-42 2K, I<43 IK.6<4S 0 0 

Tousl !174,254 636.1$09 715.320 KI 7.K9K 910.419 996.004 1.090.932 

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Table 7.8 Total Depreciation Deductions by 

TRA 86 Depreciation Class, 1986-1992 

Deereciation Class 1986 1987 1988 1989 1990 1991 1992 

IS MiUions) 

Class I (3 year) 49,630 34,429 20'.619 14,776 17,369 19.225 20.917 

Class 2 (S year) 234,107 257,076 2\U ,379 293,319 298,512 325,573 370.567 

Oass 3 (7 year) 5,174 21,191 44,778 69,757 94,397 116.204 138,841 

Class 4 (10 year) 9,306 9.577 9.11112 10.479 11,325 12,150 13.082 

Class S (IS year) 39,319 39,682 39.176 39.6911 41,223 43,1167 47,620 

Class 6 (20 year) 2.541 2,529 2,249 2,020 1.1175 1,777 1,731 

Class 7 (27 .5 year) 11 .545 13,672 15.362 17,379 19.663 22.215 25,162 

Class 8 (31. s year) 0 1.560 5,01!3 9,341 14.246 19.717 25,676 

Prior Year & Transition 21.280 41 .679 49,327 50,004 S0,695 31,581 20,733 

Total 372,902 421 ,396 467.854 506.773 549,303 592.308 664,328 

Table 7. 9 Revenue Estimates for Depreciation Schedule Changes in 

TRA 86, 1986-1992* 

1986 1987 1988 1989 1990 1991 1992 

($ MiUions) 

Calendar Year Llabilily 

Individual -84 -335 -362 57.3 1,830 3.463 3.908 

Corporate -312 - 1.356 ·2.126 -77 3.4411 11.672 9.H79 

Total -396 · 1,692 -2.4117 497 5,2711 12, 135 13,787 

Fiscal Year Receipts 

Individual 0 -210 -345 -11 1,045 2.443 3.630 

Corporate 0 - 1.126 -1.1111! -896 2,038 6,51!3 9.396 

Total 0 -1,336 -2.163 -907 3.0113 9.025 13.026 

223 

*These estimates may differ from other pubnshed estimates because they are based on a 

different economic forecast and include only selected capital cost recovery provisions. 

months). These revenue losses total about $4. 6 billion for the three calendar 

year period. These effects dissipate with time as smaller depreciation 

deductions in later years offset faster deductions in earlier years. Second, 

the large investment category of structures that receive smaller annual 

depreciation allowances under the Act increase revenue enough over a few years 

to dominate the revenue reductions on equipment. The revenue loss becomes a 

half billion dollar gain in 1989 which increases to over $5 billion in 1990. 

The total estimated revenue gain from the depreciation provisions exceeds $20 

billion over the seven year period. 
224 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

The combined effect of all depreciation and investment credit changes calculated by the depreciation model is presented in Table 7. 10 The dominant 

effect of the repeal of the investment credit insures a revenue gain in all 

years despite early period losses from increased expensing and depreciation 

allowances for many assets. These estimated revenue increases total about 

$231 billion using the post reform statutory tax rates. The Tax Reform Act 

lowered statutory tax rates which offsets much of this revenue increase. 

B. Adjustments to Depreciation Model Results 

Four adjustments to the results from the depreciation model produce the 

final set of revenue estimates. The first adjustment concerns the 35 percent 

cutback of investment credit carryforwards which are phased in over a two-year 

period. To estimate the effects of the reduction, more recent historical data 

than are contained in the depreciation model were used to determine the amount 

of unused investment credits available for carryforward at the end of 1985. 

Separate more refined estimates, including results from the Treasury corporate 

tax model, were used to determine the pattern of carryover usage, and the 

extent to which the reduction would restrict credit usage. 

Adjustments were also made to the results for the elective 15-year carryback for certain taxpayers, in particular, certain steel companies and qualified fanners. The corporate and individual tax models and an analysis of 

specific tax returns were used to determine the amount of JTC's affected by 

the provision, and the extent to which individuals and corporations would be 

able to utilize the carryback option. 

The third adjustment accounts for the tax treatment of equipment used for 

research and development (R&D) purposes. Under pre-reform law R&D equipment investments were depreciated as three year property. Under tax reform 

these investments are treated as five year property. Because the depreciation 

model does not separately identify investment for R&D purposes. it cannot 

provide estimates that adequately reflect changes in tax depreciation rules 

that apply to this use of investment. A supplemental model was employed to 

obtain an estimate of the change in revenue from the altered treatment of R&D. 

Table 7 .1 0 Summary of the Revenue Changes Associated with 

Capital Cost Recovery Provisions of TRA 86, 1986-1992* 

1986 . 1987 1988 1989 1990 1991 1992 

($ MiUionsl 

Calender Year Tu liability 13.1153 111 .870 27.741 36.1111 45.961 5K.062 59.496 

Fi~cal Year ReceiptS 0 23.997 23.11K6 30.617 41.490 !i:!.!i92 !\1!,615 

•These estimates may differ from other published estimates because they are based on a 

different economic forecast and include only selected capital cost recovery provisions. 

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The Treasury Depreciation Model 225 

which is added to the results of the depreciation model. A forecast of 

investment in R&D property is depreciated according to both pre-refonn and 

reform rules. A marginal tax rate is applied to the difference in annual 

depreciation deductions and the resulting tax change added to the model 

results for depreciation-related revenue changes. These adjustments add 

approximately $4 to $5 billion to revenue through 1992. 

This adjustment is an approximation because information on the distribution 

of tax lives of R&D property is not available. Under pre-refonn law almost 

all R&D equipment would be classified as 5 year ACRS property in the depreciation model. Under post-reform tax ruJes most R&D investment would be classified as 5 year property (computers and high technology instruments) and a 

smaller portion would be classified as 7 year (or longer lived) property. On 

average it is assumed that because of the faster depreciation method under 

reform (200 percent declining balance versus 150 percent) tax depreciation 

would not be substantially slower (or faster) under refonn than before in the 

absence of special treatment of R&D property. Thus. no net revenue increase 

would be shown in the depreciation model from the change in tax treatment of 

R&D property. The supplemental model calculation then approximately adjusts 

revenue for the change in R&D equipment depreciation rules. If all R&D property under the new rules is 5-year property the adjustment understates the 

additional revenue from longer tax lives on R&D equipment. 

The fourth adjustment is for auto and truck leasing. Although the depreciation model makes some provision for the retirement of assets or sales to nonbusiness sectors. it does not adjust depreciation allowances for recapture of 

excess depreciation when an asset is sold on the difference between the sale 

price of assets and the depreciable basis. Recapture increases revenue when 

depreciation schedules overstate depreciation and reduces revenue when depreciation is understated. In effect, recapture adjusts depreciation allowances 

to the correct total amount (neglecting inflation) when the asset is soJd. 

The Tax Reform Act changes the depreciation schedule for autos and light 

trucks from 3 years. which would generally overstate depreciation. to 5 years. 

The depreciation method also is changed from approximately 150 percent declining balance to 200 percent decJining balance (with an op~imal switch to 

straight line). For automobile and truck leasing, where the holding period is 

short in many cases and assets are often systematically resold, an adjustment 

is made to the depreciation model results for recapture. The series for 

investment in autos and trucks are divided into a leased fraction subject to 

depreciation recapture. Proportions of auto and truck investments are assumed 

to be sold each year at a price determined by a depreciation rate, assumed to 

be 33 percent for autos (Hulten and Wycoff (1981)). and an inflation rate. 

assumed to be 3 percent over the forecast period. The value of depreciation 

deductions is calculated twice both assuming no sales and assuming sales distribution patterns for autos and for trucks. The difference between these 

sale and no sale calculations of $4 billion over the period is subtracted from 

revenue estimates. The net change from this adjustment is a reduction in the 
226 Geraldine Gerardi/Hudson Milner/Leslie Whitaker/Roy Wyscarver 

estimated revenue increase in autos and light trucks that would otherwise be 

calculated for the forecast period from a lengthening of tax depreciation 

lives. 

APPENDIX 

Table 7. II compares depreciation systems under prior law and the Tax Reform 

Act of 1986. 

Table 7. l J Comparison of Depreciation Systems 

Asset ~ADR Midpoint Life or DescriEtion~ Pre-Reform Law Tax Reform Act 

2-4 3-yr ACRS 3-yr 008/SL 

R&D equipment (various ADR midpoint Jives) 3-yr ACRS 5-yr 008/SL 

Autos & light trucks (3,4) 3-yr ACRS 5-yr 008/SL 

Race horses over 2 years old 3-yr ACRS 3-yr 008/SL 

I 3-year and older horses 3-yr ACRS 3-yr 008/SL 

4.5-6.5 5-yr ACRS 5-yr 008/SL 

Semi-conductor manufacturing equipment 

(reassigned to 5-year from 6-year ADR 

midpoint life) 5-yr ACRS 5-yr DDB/SL 

Qualified technological equipment 

(various and no ADR lives) 5-yr ACRS 5-yr 008/SL 

Renewable energy property 

(various and no ADR midpoint lives) 5. 15-yr ACRS 5-yr 008/SL 

7-9.5 

Rental clothing (9) 5-yr ACRS 5-yr 008/SL 

Computer based central office-switching 

equipment (reassigned to 9.5 from 

18-year ADR midpoint life) 5-yr ACRS 5-yr 008/SL 

10-12.5 5-yr ACRS 7-yr DDB/SL 

Breeding and work horses (I 0) 5-yr ACRS 7-yr 008/SL 

No ADR life personal property 5-yr ACRS 7-yr 008/SL 

Railroad track (assigned 10-year 

ADR midpoint life) 5-yr ACRS 7-yr 008/SL 

13-15.5 . 5-yr ACRS 7-yr 008/SL 

Railroad tank cars ( 14-15) 10-yr ACRS 7-yr 008/SL 

Single purpose agriculturaJ structures 

(reassigned to IS-year from 34-year 

ADR midpoint life) 5-yr ACRS 7-yr 008/SL 

16-19.5 5-yr ACRS 1 0-yr 008/SL 

20-24.5 5-yr ACRS 15-yr 15008/SL 

Telephone distribution plant 

(reassigned 24-year from 35-year 

ADR midpoint life) 5. 15-yr ACRS 15-yr 15008/SL 

Sewage treatment plant (assigned 

24 year ADR midpoint life) 5-yr ACRS 15-yr 15008/SL 

25-21 5-yr ACRS 20-yr ISODB/SL 

21.5-29.5 5-yr ACRS 20-yr 15008/SL 

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Table 7.11 Comparison (continued) 

Asset (ADR Midpoint Life or Description) 

27.5-29.5 real property 

30-35.5 

30-35 .5 real property 

36 and over ADR midpoint life 

Sewer pipes {assigned 50-year 

ADR midpoint life) 

36 & over ADR midpoint life 

real property 

Less than 27.5 real property 

Residential housing 

Low-income housing 

Manufactured homes 

Public utility property (18 .5-24.5) 

Public utility property (25 + ) 

The Treasury Depreciation Model 227 

Pre-Reform Law 

19-yr ACRS 

5-yr ACRS 

19-yr ACRS 

5-yr ACRS 

15-yr ACRS 

19-yr ACRS 

19-yr ACRS 

19-yr ACRS 

15-yr DDB/SL 

10-yr ACRS 

10-yr ACRS 

15-yr ACRS 

Tax Reform Act 

31.5-yr SL 

20-yr 150DB/SL 

31.5-yr SL 

2Q-yr 150DB/SL 

20-yr 150DB/SL 

31 .5-yr SL 

20-yr 150DB/SL 

27.5-yr SL 

credit provided 

10-yr DDB/SL 

by ADR life 

20-yr 150DB/SL 

REFERENCES 

Fullerton, Don. Robert Gillene. and James Mackie, Investment Incentives Under the Tax Reform 

Act of 1986. Chapter 5 in this volume. 

Gorman. John A .. Musgrave. John C .. Silverstein. Gerald and Comins, Kathy A .. Fixed 

Private Capital in the United States. Survey of Current Business. Washington. D.C. (July). 

pp. 36-47, 1985. 

Hulten , Charles R .. and Wykoff, Frank C .. The Measurement of Economic Depreciation. In 

C.R. Hulten (Ed.). Depreciation. Inflation and The Taxation of Income From Capital, 

Washington, DC: The Urban Institute Press 1981 . 

Nester. Howard W.. A Guide to Interpreting the Dynamic Elements of Revenue Eslimates. 

Chapter I in this volume . 

Winfrey. Robley, Stalistical Analyses of Industrial Property Determinants Bulletin 125. 

Iowa Experiment Station, Iowa State College of Agricultural and MechaoicaJ Arts, 

Symmetrical No. 3, p. 100, 1935.