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Xerox University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106 RENNIE, Henry George, 1940- AGGREGATION THEORY, INVESTMENT BEHAVIOR AND RATIONAL LAG FUNCTIONS.

The Ohio State University, Ph.D., 1973 Economics, theory ti

University Microfilms,A XEROX Company, Ann Arbor, Michigan

© Copyright by

Henry George Rennie

1973

THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED. AGGREGATION THEORY, INVESTMENT BEHAVIOR

AND RATIONAL LAG FUNCTIONS

DISSERTATION

Presented in Partial Fulfillm ent of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By Henry George Rennie, B.Sc., M.A.

The Ohio State University 1973

Approved by ACKNOWLEDGMENTS

I t ts my pleasure to acknowledge the assistance of various persons who contributed to this study. Special thanks are due my advisers, Professors E. Bal tens per ger, W. L. L'Esperance, and

P. M attila, who gave me continual feedback throughout this study.

I should, in particular, lik e to thank Professor L'Esperance for his encouragement from the inception to the completion of this study.

An essential part of a study of this type is computer programming and I would lik e to thank my very competent assistants,

Molly Garrett, Paul Hart, Andrew Hochstein, and John Irmen. To my typists, Mary Jane Donaldson, Mari Kanavel, and Carol Kaufman, thank you.

The sacrifice involved in reaching the final product was borne by my family. To Heather, who went from speaking no English a t a l l , to saying, "daddy is making book," to, "is your dissertation finished, father?" and to Matthew who was apparently oblivious to it a l l , T.K.& H. And to my w ife, Phoebe, for her encouragement, thank you.

11 VITA

8 October 1940 Born - Greenock, Scotland, Gt. Britain

1963 ...... B.Sc., The Ohio State University, Columbus, Ohio

1964 ...... Research Assistant, Bureau of Business Research, The Ohio State University, Columbus, Ohio

1965 ...... M.A., The Ohio State University, Columbus, Ohio

1965-1969 . . . Teaching Associate, Department of Economics, The Ohio State University, Columbus, Ohio

1969-Present. Assistant Professor, Department of Economics, The University of Toledo, Toledo, Ohio

PUBLICATIONS

"Bayesian probability and the General pascal Distribution," American Statistical Association, Proceedings of the Business and Economic Section, 1972, 431-434.

FIELDS OF STUDY

Monetary Theory and Policy

Econometrics

International Trade and Development

11 f TABLE OF CONTENTS

Page ACKNOWLEDGMENTS ...... i i

VITA ...... , ...... 1ii

LIST OF TABLES...... vi

LIST OF ILLUSTRATIONS...... 1x

INTRODUCTION ...... 1

Chapter

I . AGGREGATION BIAS IN RATIONAL LAG FUNCTIONS ...... 7

1. Aggregation and the aggregation problem 2. The meaning of "consistent aggregation" 3. Necessary and sufficient conditions for consistent aggregation 4. Approaches to the aggregation problem 5. The analogy approach to aggregation 6 . The relations between micro and macro parameters 7. A measure of the aggregation bias in macro-parameters 8 . The concept of a distributed lag 9. The rational lag function 10. The general Pascal distributed lag function 11. Parameter bias in rational lag forms 12. The relation between the estimated and the implied macro-parameters in rational lag functions 13. The effect of aggregation on the lag.structure and moments of a general Pascal lag function 14. Aggregation, minimum residual variance and model choice

II. INVESTMENT...... 48

1. Introduction 2. Generalized accelerator mechanism 3. Theories of capital demand 4. Replacement investment 5. Models of Investment behavior

1 v Chapter Page

I I I . ESTIMATION OF A RATIONAL LAG FUNCTION...... 6 8

IV. EMPIRICAL: INVESTMENT THEORY PERFORMANCE...... 75

1. Introduction 2. The sample 3. Measurement 4. Micro performance 5. Macro performance

V. EMPIRICAL: AGGREGATION BIAS...... 103

1. Bias is the unconstrained macro coefficients 2. Bias in the lag structure and average lag 3. Bias in the aggregate residual variance 4. Bias and theory selection 5. The empirical literature: A comparison of findings

VI. SUMMARY AND CONCLUSIONS...... 169

1. Summary 2. Conclusions

APPENDIX

A. . 177

B...... 211

C...... 224

D...... 231

E...... 238

F...... 261

G...... 265

H...... 277

1...... 284

J...... 288

BIBLIOGRAPHY...... 295

V LIST OF TABLES

Table Page

1. Components of bias in the estimated aggregate parameters of a rational distributed lag function ...... 37

2. Sample firms, their ranking by sales, assets, and net income, and th eir OBE-SEC industry group ...... 77

3. Size distribution of firms within groups by average investment and capital stock ...... 78

4. Calculated replacement coefficients for twenty-seven firms and six industry groups ...... 82

5. Goodness of f it statistics-firms ...... 90

6 . Number of times, out of twenty-seven, a theory had a lower standard error than competing theories .... 96

7. Number of desired capital stock coefficients and number at least twice th eir standard errors for twenty-seven companies ...... 98

8 . Goodness of f it statistics-aggregates ...... 100

9. Number of times, out of six, a theory had a lower standard error than competing theories ...... 101

10. Number of desired capital stock coefficients and number at least twice th eir standard errors for six aggregates...... 1 0 2

11. Test results of parameter vector homogeneity by theory and group...... 108

12. Average size of |(E-T)/E| over six industries by theory and coefficient ...... 114

13. Analysis of variance of |(E-T)/E| over six industries by theory and coefficient ...... 117

14. Analysis of variance of T/E by theory and coefficient. . 118

vi Table Page

15. Analysts of variance of average [E-T| over five theories by bias component and coefficient .... 1 2 0

16. Analysis of variance of E-T by corresponding-noncorresp- onding components and coefficient ...... 121

17. statistics-firms ...... 124

18. Autocorrelation statistics-aggregates ...... 129

19. A summary of results using the Durbin-Watson statistic by theory and level of aggregation ...... 130

20. A summary of results using Durbin's h statistic by theory and level of aggregation...... 134

21. Analysis of variance of T/E by estimator (OLS and D-TSLS) and c o e ff ic ie n t ...... 137

22. Analysis of variance of T/E by bias component and constrained coefficients ...... 141

23. Estimated and true lag structures and th eir bias by industry group. Neoclassical I and I I theories . . 143

24. Average lags and proportion of investment completed after two years for various values of B4 and consistent with a general Pascal lag ...... 149

25. Sign of the differences between the estimated and true aggregate residual variances by theory and industry . 153

26. Ratio of the estimated to the true aggregate residual variance, ^ /{U 'U /T ), by theory and industry . . . 154

27. Analysis of variance of ^/(L I'U /T ) by theory and industry ...... 155

28. Ratio of the bias components to the estimated aggregate residual variance ...... 156

29. Average of the absolute values of the ratios of the components to S 2 ...... 158

30. Number of times, out of six, a theory had a lower standard error than competing theories by true and estimated residual variance...... 159

v ii Table Page

31. Investment theories ranked by true and estimated residual variance...... 160

32. Kendall's t correlation of the true and estimated rankings of five investment theories ...... 161

33. Ratio of the components of the aggregate estimated coefficients to E. Boot-DeWIt ...... 163

34. Ratio of the components of the aggregate estimated coefficients to E. Gupta ...... 166

35. Kuh's equation f o r m s...... 167

36. Ratio of the true to the estimated aggregate coefficients. K uh ...... 168

v iii LIST OF ILLUSTRATIONS

Figure Page

1 . 95% confidence ellipse from constrained estimates of B4 and Bg. Neoclassical I ...... 146

ix INTRODUCTION

1. Micro theory and macro data: The aggregation problem

I t frequently happens in economics that several competing the­

ories exist to explain an economic variable. Fixed capital invest­

ment behavior is a case in point where there are at least four compet­

ing theories ... accelerator, expected profits, liquidity, and neo­

classical J Each theory and its variations has been proposed and def­

ended as explaining movements in fixed capital investment; however, a

gap exists between these theories and their empirical testing. While

the theories are developed at the micro or individual firm level they

are quite often tested at a more aggregative or industry level. 2

Usually this is done without any discussion of or ju stificatio n for

the rationale of applying a theory of individual firm behavior seriatim

at the aggregative level.^

^These theories are discussed in Chapter I I .

^See Robert Eisner, "A Distributed Lag Investment Function," Econometrica. XXVIII (January, I960), 1-29; W. H. L. Anderson, Corpor­ ate Finance and Fixed Investment (Boston: Division of Research, Grad­ uate School of Business Administration, Harvard University, 1964); Dale W. Jorgenson and James A. Stephenson, "Investment Behavior in U. S. Manufacturing, 1947-1960," Econometrica, XXXV (April, 1967), 67- 89; J. R. Meyer and R. R. Glauber, Investment- Decisions, Economic Fore­ casting, and Public Policy (Boston: Division of Research, Graduate, School of Business Administration, Harvard University, 1964).

^For example, C. E. Ferguson in his excellent book The Neo­ classical Theory of Production and Distribution (Cambridge: Cambridge University Press, 1969) says at the outset, "But the macroeconomic theory discussed is the macroeconomic theory constructed by analogy with the corresponding microeconomic theory," 5. 1 Economists are aware that traversing the ground between a well developed micro theory and a postulated analogous macro theory is an act of fa ith . The assurance which would come from proving that a specific set of micro equations implies an analogous macro equation is absent in the theory of investment behavior.^ R. M. Solow takes a very expedient attitude when he says:

"Before going on* le t me be explicit that I would not try to ju s tify what follows by calling on fancy theorems on aggregation and index numbers. Either this kind of aggregate economics appeals or i t doesn't. Personally I belong to both schools. If i t does, I think one can draw some crude but useful conclusions from the results."5

Economic theory can explain or predict only when confronted with empirical data. The paucity of the data at the individual (firm, consumer, e tc .) level necessitates the use of grouped data. The method of aggregation then becomes important. We shall discuss some aggregation methods in Chapter I; however, a fundamental problem common to most methods is that the micro and macro empirical results

^ It is not absent in the theory of consumer behavior. I t can be shown "that i f the prices of a group of goods change in the same proportion, that group of goods behaves as i f i t were a single commo­ dity." See J. R. Hicks, Value and Capital (2d ed.; Oxford: , 1946), 312-3T3. Also, Paul A. Samuel son, Foundations of Economic Analysis (Cambridqe: Harvard University Press, 1$47), l4T- m — ------—

5r. M. Solow, "Technical Change and the Aggregate Production Function," Review of Economics and Statistics, XXXIX (Auqust, 1957), 312. are inconsistent . 6 That is, knowledge of the individual relations and

their arguments w ill not usually imply the same value of the aggregate

dependent variable as w ill knowledge of the aggregate relation and its

arguments. The consistency conditions (discussed in 1.4.) are so

severe that they are seldom satisfied in practice.^ The practical question then becomes one of determining, empirically, the magnitude of the errors created by aggregation.

2. Purpose and scope of this study

It is common practice among economists to select one theory over competing theories on the basis of minimum residual variance of

a regression (or maximum R^).® Indeed, i t has been shown that the

estimated residual variance of an incorrect maintained hypothesis w ill

be larger than that of a correct alternative hypothesis; 9 however, 1 t

appears not to have been recognized that i f the hypotheses refer to

aggregated data, the test is innappropriate because the estimated

6The phrase "consistent aggregation" appears to have been fir s t used by M. McManus in "General Consistent Aggregation in Leontief Models," Yorkshire Bulletin of Economic Research, V III (June, 1956), 28-48. The concept of consistent aggregation is explored in Chapter I where a rigorous definition is presented. In addition, various def­ initions of consistency are quoted and shown to be essentially the same, albeit a loose paraphrasing, of the rigorous definition. A distinction can be made between "totally consistent" and the less restrictive "partially consistent" concepts in Yuji Ijir i, "Funda­ mental Queries in Aggregation Theory," Journal of the American Stat­ istical Association, LXVI (December, 197l), 766-782.

^For the necessary and sufficient conditions for consistent aggregation and th e ir derivation, see Andr£ Nataf, "Sur la Possibilite de Construction de Certaines Macromodeles," EcOndmetrica, XVI (July, 1948), 232-244. These conditions are presented in Chapter I. aggregate residual variance is biasedThus, there will be errors

in model selection pertaining to micro data i f these models are

selected using the minimum residual variance of aggregate data. One

purpose of this study w ill be to determine the size of the error in

the aggregate residual variance.

Nataf's paper^ has shown that micro and macro parameter

estimates w ill be inconsistent unless a ll parameters for a given

variable are identical. This study, after specifying a "true" aggreg­ ate parameter, w ill measure the size of this aggregation bias. Micro

and macro structures will be chosen from the rational distributed lag

class of functions . ^ 2

8As an example, see Dale W. Jorgenson and Calvin D. Siebert, "A Comparison of Alternative Theories of Corporate Investment Behavior," American Economic Review, L V III (September, 1968), 681-712.

^Henri Theil, Economic Forecasts and Policy (2d ed.f rev.; Amsterdam: North-Holi and, 1961 ), 326-334.

10I t w ill be shown in Chapter I that the sample variance of the estimated macro disturbance equals a "true" sample variance plus the sum of the variances and co-variances of aggregation bias com­ ponents. Thus, a model selected over competing models using the minimum residual variance criterion at the macro level w ill not necessarily be the same model, selected on the same basis, i f the micro data were available.

^N ataf, Econometrica, XVI.

12'The rational lag function is discussed in Chapter I. Est­ imation problems and techniques are discussed in Chapter I I I . For the development of the rational lag function, see Dale W. Jorgenson, "Rational Distributed Laq Functions," Econometrica, XXXIV (January, 1966), 135-149. I f the micro and macro parameters are constrained to conform to those of a general Pascal distributed lag function^ we shall be interested in the errors among the estimated aggregate, "true" aggre­ gate, and individual lag structure and average lag.

The scope of this study is limited to a specific set of com­ peting theories . . . those of fixed capital investment behavior. A spirited debate is taking place in the current economic literature as to which of four investment theories is correct . . . the accelerator, the expected profits, the liquidity, or the neoclassical th e o r y .^

We shall review these theories in Chapter I I and c ritic a lly assess th eir empirical performance in Chapter IV. 1 5 These theories are used solely as a vehicle for application of the concepts developed in

Chapter I which concepts have wider applicability than to the field of investment behavior.

The study is further confined to a specific set of micro and macro functions. Specifically, to the class of rational lag funct-

13 Jorgenson, Econometrica, XXXIV, 135-149.

^Jorgenson and Siebert, American Economic Review, L V III, 681-712.

^The reader is referred to Dale W. Jorgenson, "Econometric Studies of Investment Behavior: A Survey," Journal of Economic Literature, IX {December, 1971), 1111-1147 fo r a review of empirical studies in fixed capital investment. This a rtic le is reviewed in Chapter I I . ionsJ6 This is not a severe constraint for two reasons: (a) The class of rational lag functions subsumes those of the finite, arith­ metic, geometric, and Pascal as special cases; (b) the theory of aggregation bias developed applies to non-distributed lag functions as well as to distributed lag functions. Estimation of the rational lag function is discussed in Chapter I I I . ^

Answers to these problems are relevant to three, not necess­ a rily mutually exclusive, groups of persons: The policy maker; the theorist; and the empirical economist.

The policy maker as forecaster and controller is interested in the magnitude, speed, and s ta b ility of policy variable changes on investment. I f the results of the model d iffe r greatly because of aggregation bias or because of incorrect model choice then his results are misleading.

The economic theorist is also interested in answers to the .• above three questions. The wide debate in the literature concerning the merits of various competing investment theories w ill be largely settled by empirical performance. Although aggregation affects this performance, very l i t t l e discussion of the direction or extent of this lft effect has yet taken place in the literatu re of investment behavior. 10

^Jorgenson, Econometrica, XXXIV, 135-149.

l^See Phoebus J. Dhrymes, Distributed Lags: Problems of Estimation and Formulation (San Francisco: Holden-Day, 1971), Chapter 9 for a discussion of the problems of estimating the parameters of a rational lag function.

18See 0. C. 6 . Boot and G. M. DeWit, "Investment Demand: An Empirical Contribution to the Aggregation Problem," International Economic Review, I (January, 1960), 3-30 who measure the dlhdttlbn ana extent of aggregation bias for ten heterogeneous firms, one investment theory (expected p ro fits ), and non-distributed lags. This article w ill be reviewed in Chapter V, CHAPTER I

AGGREGATION BIAS IN RATIONAL LAG FUNCTIONS

1. Aggregation and the aggregation problem

The term "aggregation" refers to the process of reducing a set of quantities and/or relations to a smaller set of quantities and/or relations. 1 For example, we may wish to aggregate demand functions for each commodity and each consumer in the U. S. into a macro consump­ tion function for the entire economy; or, we may wish to aggregate investment functions for individual firms into an industry investment function.

Having defined the ter’m "aggregation" we now explain what is meant by the phrase "the aggregation problem." This phrase is used by

^ h is is the essence of definitions of the term "aggregation" given by: Lawrence R. Klein, "Macroeconomics and the Theory of Rational Behavior," Econometrica, XIV (A pril, 1946), 93; E. Malinvaud, Statistical Methods of (Chicago: Rand McNally, 1966), 118; Kenneth May, "The Aggregation Problem for a One-Industry Model," Econometrica, XIV (October, 1946), 285; Kenneth May, "Technological Change and Aggregation," Econometrica, XV (January, 1947), 51.

2See R. G. D. Allen, Mathematical Economics (2d ed.; London: Macmillan, 1966), Chapter 20 which is entitled "The Aggregation Problem" and in particular section 20.1 which is entitled "The Problem"; T. M. Brown, Specification and Uses of Econometric Models (London: Macmillan, 1970)^ Section 8.2 is entitled "The Nature of the Mathematical Problem of Aggregation"; H. Theil, Linear Aggregation of Economic Relations (Amsterdam: North-Holi and, 1954), section 1 ."I is entitled "Aspects of the Problem." I t is not implied here that the authors were solely or even generally concerned with the consistency of aggregation but a ll start by recognizing i t as "the problem." As I j i r i says, "total consistency is the most basic problem in aggregat­ ion theory." See Yuji I j i r i , "Fundamental Queries 1n Aggregation Theory," Journal of the American S tatistical Association, LXVI (December, 19/1), 756. 7 many authors, for example Allen, Brown, and Theil, 2 and refers to the fact that the results of aggregation are generally inconsistent,

While a rigorous definition of consistency w ill be presented in section 1.3. i t w ill be helpful to present an in tu itiv e discussion of the aggregation problem at this point.

Aggregation involves relationships between three sets of functions: (a) A set of functions for individuals (firms, consumers, etc .) relating an endogenous variable to exogenous variables. For example, the set of individual demand functions or the set of firm investment functions in the above examples. I f we assume J indiv­ idual functions in K variables we may write the jth individual equat­ ion as: f1*1*) yj = V xl j xKj) [j[ " ]■ ***’ jjj

(b) A set of functions relating the aggregate variables to the underlying individual variables:

( 1 . 2 .) x^ - X(^ (x|^*|, . . . iX|^j) (j — 1 , . . . ,J) (k = 1 , . . . ,K)

(1.3.) y " y(yj, ... »yj) (j ~ 1» ••• »J) (k — 1 , . . . , K)

(c) An aggregate function relating the aggregate variables:

(1.4.) y ■ Ffx'j, ... »X|^)

The above four equations define ah aggregation structure which consists of a microsystem ( I . I . ) , a macrosystem (1 .4 .), and aggregation functions (I.2-1.3.). To understand the nature of the aggregation problem we refer to the following schematic diagram of an aggregation structure:.4

(d = 1, ... ,J) (k = 1, ... ,K)

{xk} -

where: {*kj ) s micro exogenous variables.

{y j> = micro endogenous variables.

{xk> = macro exogenous variables.

{y} = macro endogenous variables,

f j = microrelation.

F = macrorelation.

*k = aggregation function fo r the exogenous variables, y = aggregation function fo r the endogenous variables.

From the aggregation structure schematic, we can see that given the micro-variables {xkj, yj> and microrelation fj as well as the aggregating functions xk, y we have defined the macro-variables

yd. There is thus an implied relation between {x^} and {y}. I f , in addition, we explicitely relate {x^} and {y} independently of F it

^ I j i r i , Journal of the American Statistical Association, LXVI. 766.

4 I j i r i , Journal of the American Statistical Association, LXVI, 768. 10 would be unlikely that the two functions (Implicit and explicit) would

be identical. The implicit and explicit functions would be inconsist­

ent. The same problem of inconsistency would arise i f we allowed the

macro endogenous variable (y> to be implied by the micro variables

{xkj» y j) and relation f j and aggregating function y while indepen­

dently specifying a macrorelation F and exogenous aggregating function

y -

2. The meaning of "consistent aggregation"

The adjective "consistent" is not used by all authors. Some

choose to use words such as exact, intrinsic, perfect, or totally C consistent. Be that as it may, we shall now present definitions of

consistency by various authors.

1. Green says, "Aggregation w ill be said to be consistent when the use of information more detailed than that contained in the aggregates would make no difference to the results of the problem a t hand. " 6

2. Fisher says, "... the term 'exact simplification' is used here to describe the situation where the detailed data X and the simplified data K coincide and there is no loss."7

3. I j i r i says, " . . . i f an aggregation structure is to ta lly consistent, the behavior of the microsystem can be completely identified from the behavior of the macro­ system . " 8

5Walter D. Fisher, Clustering and Aggregation in Economics (Baltimore: Johns Hopkins Press, 1969), uses the term "exact." TFTeil, Linear Aggregation, uses"perfect." I j i r i , Journal of the American Statistical Association, LXVI, uses "totally consistent."

6 H. A. John Green, Aggregation in Economic Analysis (Prince­ ton: Princeton University Press, 1964), 3.

^Fisher, Clustering and Aggregation in Economics, 18.

8 I j i r i , J. of the American S tatistical Association, LXVI, 766. 11

Whether the definition of consistency 1s expressed in the language of information theory via loss functions or in the language of deductive logic they are a ll saying the same thing. An aggregation structure consisting of a microsystem, a macrosystem, and an aggreg­ ation function is consistent if it contains no formula such that both the formula and its negation can be derived from the structure. 9

3. Necessary and sufficient conditions fo r consistent aggregation

Are the four functions (I.1 .-I.4 .) consistent? Is the analogy approach to aggregation consistent? In the process of answering these questions we shall rigorously define what is meant by "consistent."

Nataf^ 0 derived the necessary and sufficient conditions fo r the aggregation of the individual functions ( 1 . 1 .) to the aggregate function (1 .4 .). According to Nataf's Theorem^ necessary and suff­ icient conditions for the aggregation of the functions ( 1 . 1 .) to the function (1.4.) are that there exist functions G, H, g^, hj, G^, Hj,

^kj* suc^ that:

9This is the Post criterion for consistency and is one of four properties of formal deductive systems. See Irving M. Copi, Symbolic Logic (2d ed.; New York: Macmillan, 1965), 180.

l^Andre Nataf, "Sur la Possibilite de Construction de Certalnes Macromodeles," Econometrica, XV (July, 1948), 232-244.

^See Green, Aggregation in Economic Analysis, 36-38 for a statement and proof of this theorem. (1.5.) y a H[h1 (y 1) + . . . + hj(yj)3 = G[gj(xj) + ... + gk(xk)] where: = HjChi j ( xl j ) + ••• + hKj^xK j^ and xk = G[gkj(xkj) + ... + 9kj(xkj)3

for (j = , *... ,J) and (k= 1 , . . . ,K)

What do Nataf's conditions mean for linear aggregation?

According to Nataf's Theorem there must exist functions G, H, gk» hj,

Gk, Hj, gkj, hkj satisfying the equation (1.5.). Thus, for linear aggregates we can re-w rite equation (1 .3 .) as:

(1 .6 .) y = y(y-), ... ,yj) = zy. = H[zhj(yj)]. J J

Similarly, we can re-write equation (1.2.) as:

(I<7*) xk = xk(xk l xkj) = *;xkj " Gk^ 9 kj^xk j^ * J u

I f equation (1 .1 .) Is linear we can deduce the functions Hj and hkj =

( 1 . 8 .) yj “ fjUij. ... “ aj + Jbkjxkj K

Hj^ hkj^xkjJ3.

Finally, if equation (1.1.) is linear we can deduce the func­ tions G and gk from equations (1.1.) and (1.3.):

(1 .9 .) y = Eyj = saj + ZSbkxkj . J J JK 13

We conclude, therefore, that the necessary and sufficient

conditions for consistent aggregation of a set of Individual firm

investment functions into an industry investment function are that

the individual functions must be linear with identical slopes.

4. Approaches to the aggregation problem

Various approaches to the aggregation problem have been pro­

posed. These approaches d iffe r in their handling of the four equat­

ions ( I .1 .- I . 4 . ) discussed above. The consistency approach to aggre­

gation places primary importance on the consistency of these four equations. 12 For example, Klein1 3 takes a micro-theory and certain

properties which the macro-theory must f u lf i ll as given. The prob­

lem then is to construct consistent aggregates of the micro-variables.

May 1^ starts with a micro-theory and aggregates, then poses the question of what macro-theory is consistent with them.

^There is a difference between consistent aggregation and the consistency approach to aggregation. Consistent aggregation, referring to the final result of an aggregation structure determines if both a formula and its negation can be deduced from an aggregation structure. On this, see section 1.9. The consistency approach to aggregation is concerned with the derivation of variables and/or relations which are consistent with other parts of an aggregation structure. On th is, see the difference between May and Klein (presented below) where i t is shown that two different structures are developed following the con­ sistency approach but are both (internally) consistent.

1 3 Klein, Econometrica, XIV, 93-108.

1 4 May, Econometrica, XIV, 285. Theil1 5 begins his theory of aggregation by stating that while

the Klein and May approaches lead to consistent aggregation they

happen not to be the commonly used methods of aggregation. He

therefor presents the analogy approach to aggregation. From a given micro-theory and the aggregates which are simple or weighted sums of

the micro-variables he constructs a macro-theory by analogy. For example, i f an individual firm 's investment demand is a function of changes in desired capital stock then we would postulate that the

industry investment demand is a function of the sum of the firms change

in desired capital stock. As mentioned in the Introduction to this study, this appears to be the most common approach to aggregation although i t is seldom exp licitely stated. I t is the analogy approach which we wish to explore in this study.

5. The analogy approach to aggregation

Theil^ 6 begins his study of the analogy approach by aggregat­ ing over one set of individuals. We shall follow his analysis in this section but recast the relations in the convenient matrix notation of KloekJ7

Let us assume that micro economic theory determines a function­ al relationship between a set of variables. We shall not be concerned

l 5 Theil, Linear Aggregation of Economic Relations.

1^Thei1, Linear Aggregation of Economic Relations.

1 7 T. Kloek, "Note on Convenient Matrix Notations in M ulti­ variate Statistical Analysis and in the Theory of Linear Aggregation," International Economic Review, I I (September, 1961), 351-360. 15 at this point with the economic content of the theory but merely state that we have a set of J linear relations for J individuals (firms, consumers, e tc .):

( 1 . 1 0 .) Yj * xjBj + Uj = 1 ...... where: Yj a a (Txl) vector of dependent variables for the jth relation.

Xj = a (TxK) matrix of exogenous variables for the jth relation.

Bj - a (Kxl) vector of unknown parameters for the jth relation.

Uj = a (Txl) vector of random elements with zero expectation for the jth relation.

We introduce the analogous aggregate relationship:

(I.11.) Y = XB + U with Y and X defined as the simple sum aggregates:

(1.12.) Y = 2Y- = a (Txl) vector of the aggregated dependent J J variable over the J relations.

(1.13.) X = SX,* = a (TxK) matrix of aggregated independent J variables over the J relations. and B = a (Kxl) vector of unknown parameters.

U = a (Txl) vector of random elements with zero expectation.

The above four equations describe, as Allen succinctly states,

"the translation of linear micro-relations into a linear macro-relation lfl by means of linear aggregates."

^BAllen, Mathematical Economics, 696. 16

6 . The relations between micro and macro-parameters

The above consistency conditions are very re stric tiv e. What i f the individual parameters are not Identical? What aggregation error does the analogy approach imply? In short, how are the parame­ ters of the aggregate relationship ( I . 11.) related to the parameters of the underlying micro relations (I.10.)? Our purpose in this section is to relate the aggregate parameters, B, to the individual parameters,

To relate B to Bj we introduce a set of auxiliary equations in which each variable in the Xj matrix is a linear function of all the aggregate independent variables:

(1.14.) Xj = XDj f Vj (j = 1, ... ,J) where: Xj = a (TxK) matrix of exogenous variables in the jth relation.

X = ZXj = a (TxK) matrix of aggregated independent variables J over the J relations.

Dj = a (KxK) matrix of auxiliary coefficients relating each variable in Xj to all variables in X.

Vj = a (TxK) matrix of residuals J 9

I f we solve for Dj by the method of least-squares we get:

-1 (1.15.) Dj = (X'X) X'Xj

We note that the least-squares estimate of B is:

-1 (1.16.) ti = (X'X) X'Y

^9The residuals, Vj, are non-stochastic due to our assumption that X j, and hence X, is non-stochastic. 17 and that:

"1 (1.17.) B = E(B) = E[(X'X) X'Y] by the assumption that E(U) = 0.

Substituting equations (1 .1 2 .), ( I . 10.). and (1.15.) in (1.17.) we get:

-I (1.18.) B = E[(X'X) X'E (XjBj + Uj)] = EDjBj. J J What meaning is to be attached to equation (1.18.)? First, the macro-parameters, B, are those implied by the macro-relation

( I . 11.) and the specified aggregates ( I . 12.- I . 13.). Second, the macro­ parameters, B, are functions of the underlying micro-parameters, Bj.

But what is the nature of these functions?

To answer the above question, we expand equation (1.1 8.):

V ^ llj D12j ... Dlkj ... D1Kj b2 °21 j B2j * = SD.B-- = Z • * * J 3 3 J • * * • • ... DKkj ... DKKj< bk. ?Klj °K2j ?Kj.

The matrix Dj are the least-squares parameters of the regression of

Xj on X. That is , for a given firm ( j ) we regress each variable

(column) of Xj on all the variables in X. Thus, Dgkj represents the coefficient of the regression of the kth micro-variable of the jth firm on the gth macro variable. I t follows from this that the fir s t row in Dj is the set of constants from each regression. 18

We can now write the implied intercept term as:

(1.20.) B1 “ £Dlk jBkj ft • • • f K J 0

The implied aggregate slope parameter is:

Bk = j j DgkjBkj ,K .K • J

These results must be disappointing to a macro-economist.

First, the implied macro-parameters are specific to the period of time covered by the data. Even i f the micro-parameters, B-, remain J unchanged outside the sample period, the implied macro-parameters may change. This is so because the macro-parameters, B, depend on Dj which in turn depends on the micro-variables, Xj. Therefor, if the relation between X- and X changes outside the sample period but B-: J J remains unchanged we can have changes in the macro-parameters.

A second problem with the implied macro-parameters is that they are functions not only of the corresponding micro-parameters but of the non-corresponding micro-parameters as well. That is , the Bkth macro-parameter is a function not only of the corresponding micro­ parameters, Bkj (j = 1, . . . ,J) but of the non-corresponding micro­ parameters Bgj (g f k, g - 1, ... „K), (j = 1, ... „J). A welcome exception is that the micro constants do not affect the implied macro slope parameters. 19 7, A measure of the aggregation bias 1n macro-parameters

Equation (1.18.) relates the aggregate parameters to the under­ lying micro-parameters. For consistent linear aggregation, the corres­ ponding micro slope parameters must be identical. 2 0 Thus, a measure of aggregation bias in macro-parameters could be derived from the definition of consistency and the actual relationship between the macro and micro-parameters. The implied macro-intercept term in equation (1.20.) can be written as the sum of the micro-intercepts plus certain covariance terms:2^

(1.22.) B] = EB-| j + JjCov(BkjDlkj ) (k = 2...... K) J K ( j = 1 * • •« »J)

The implied macro slope parameters in equation (1.2 1.) can be written as the average of the corresponding micro slope parameters plus certain covariance terms : 2 2

i (1.23.) Br, = J EBl.., + J 2Cov(BifiDaki) (k =2 ...... K) J K 3 9 3 (g - 2 K ( j - 1...... J)

Theil has shown that it is always possible, by a suitable type of fixed weights aggregation, to obtain consistency between the micro

20Using Nataf's definition of consistency. See section 1.3. Also, for the same result see; Allen, Mathematical Economics. 709; Green, Aggregation in Economic Analysis, 40; Theil, Linear Aggregation of Economic Relations, 142.

2 ^Theil, Linear Aggregation, 16; Allen, Mathematical Economics, 711.

22Thetl, Linear Aggregation, 16. 20 and macro equations. That is , " if aggregation is performed such that a ll microvalues . . . are weighted proportionally to th eir microparame­ ters . . . both the intercept . . . and the rates of change . . . of the macro-equation depend on corresponding microparameters only."23

Our purpose in this study is not to obtain consistent aggre­ gation but, rather, to measure the errors when linear aggregates are used. Thus, if we define the "true"2^ macro-intercept as:

(1.24.) 2 B-| j (j = 1...... J) J then the aggregation bias of the macro intercept is:

(1.25.) JSCov(BkjDlkj-) (k = 2...... K) K ( j = 1, . . . »J)

I f we define the "true" macro slope parameter as:

(1.26.) UBkj* (k = 2, . . . ,K) JJ (j — 1 , . . . |J) then the aggregation bias of the macro slope parameter is :2®

(1.27.) JZCov(BkjDgkj) fk = 2, . . . ,K) K (g - 2 ...... K) (j = 1 J)

We can separate the aggregation bias into a bias attributable to corresponding and non-corresponding micro-parameters. F irs t, we re-w rite the covariance terms of both the intercept and slope parame-

^3 Theil, Linear Aggregation, 18.

2^The word "true" was used by J. C. G. Boot and G. M. DeWit, "Investment Demand: An Empirical Contribution to the Aggregation Problem," International Economic Review, I (January, 1960), 3-30. 25Note that absence of aggregation bias does not imply consis­ tency using Nataf's definition of consistency as explained in section 3. 21 ters equations (1.25. and 1.26.):

(1.28.) 0Kc°v (DkgjBgj > - ® kgjBgJ - 0DkgBg ■ 1. ... ,K] = 2, ... ,Kj [j - 1 , . . . ,JJ where DjJg = 1ZDkgj and B* = lEBgj JJ Now, since^®

(1.29.) J1 SDka1B; 0 TJ kgJ 9

LB*KJ

Then, combining equations (1.28.) and (1 .2 9 .), we get the aggregation bias of the macro-intercept:

(1.30.) ( g = 2 ...... K) (4 = 1...... 0) and the aggregation bias of the macro slope parameters:

(1.31.) Jk.... =.2 ...... K] iDkgjBgj " Bk [g = 2 , . . . ,K [j = 1, ... .J]

26We make use of the fact that z D.,- 0 0 ., 0 J Kg 1 0 .. 0 0 1 0 0

0 ... 1.

See Allen, Mathematical Economics. 710. 22 The aggregation bias of the macro slope parameters attributable

to the corresponding micro-parameters 1 s:

(1.32.) £°kkjBkj " Bk (j * 1* *" *jj while the aggregation bias of the macro slope parameters attributable to the non-corresponding micro-parameters is:

(1.33.) £BkcHBai (k s 2» . . . ,K) J K9J 9J (g * 2.. . . . |K) jk t g) (j - 1 , . . . »J)

I t w ill be noted from equation (1.30.) that the entire aggreg­ ation bias of the macro-intercept is attributable to the non-corres­

ponding micro-parameters.

8 . The concept of a distributed lag

The concept of a lag in economics is required whenever a cause

in one time period has its effect in another (future) time period.

If the total effect of one variable on another does not take place in

the same (future) time period we refer to this as a distributed lag effect.

We may write a distributed lag function as:

( 1 . 3 4 .) Yt =sJjwsXt _s where and Xt are observed values of the dependent and independent

variables at time t and the ws are the unknown parameters.

For estimation we impose the requirement that a fin ite change 23 in the independent variable results in a fin ite change in the depen­ dent variable:

(1.35.) sҤws = ^ +0I>

A more restrictive constraint is:

(1.36.) s=ows = ®

9. The rational lag function

Several authors of distributed lag schemes have been motivated by their desire to approximate the in fin ite lag model (1.34.) with a more manageable model.2? They have generally sought...

(a) "To approximate the true lag coefficients closely.

(b) To do so with as few parameters as possible, while keeping the estimation scheme relatively simple."28

2?For example, the geometric lag model is an approximation to (1.34.) by replacing the infinite set of coefficients, ws, by two par­ ameters, a, b, where ws = abs, s = 0 ,1 ,2 , . . . , 0