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8
The Classification of Occupations: A
Review of Selected Systems
THE CLASSIFICATION STRUCTURE OF THE DOT
The purpose of the DOT occupational classification system is to organize
occupations into groups that are similar in the sense that they tend to make
similar demands on workers or in which workers with specific qualifications or
characteristics are likely to find satisfactory employment. The first edition DOT
noted in its foreword (p. xi):
As a product of the [Employment Service] Research Program, [the DOT] is
part of a directed effort designed to furnish public employment offices in this
country with information and techniques that will facilitate proper classification
and placement of work seekers.
Getting qualified workers into appropriate jobs is a task that can be done
most adequately when the transaction is based on a thorough knowledge of both
worker and job…. Thus, it becomes part of the duties of public employment
offices to learn as much as possible about jobs and workers in order to be able
to act as an effective placement agency. If a foundry superintendent wants the
public employment office to send him a cupola tender, the office must know
enough about the work and worker to be able to refer a registrant who has been
previously classified as qualified and capable of doing the work required.
The DOT was developed to provide Employment Service interviewers and
counselers with the information necessary to classify workers and jobs
appropriately in order to match them.
The fourth edition DOT reflects the continued primacy of job-worker
matching as the reason for its existence. The first sentence of its
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introduction lists job matching as the primary justification for producing the DOT
(p. xiii):
The Dictionary of Occupational Titles is an outgrowth of the needs of the
public employment service system for a comprehensive body of standardized
occupational information for purposes of job placement, employment
counseling and occupational and career guidance, and for labor market
information services. In order to implement effectively its primary assignment
of matching jobs and workers, the public employment service system requires a
uniform occupational language for use in all its offices. This is needed to
compare and match the specifications of employer job openings and the
qualifications of applicants who are seeking jobs through its facilities.
CREATING OCCUPATIONAL TITLES
The process by which the millions of jobs in the economy are grouped into
the occupational titles in the DOT is crucial in determining the usefulness of the
DOT as a matching tool. The fourth edition DOT describes this process in general
terms (p. xv):
Work is organized in a variety of ways. As a result of technological,
economic and sociological influences, nearly every job in the economy is
performed slightly differently from any other job. Every job is also similar to a
number of other jobs.
In order to look at the millions of jobs in the U.S. economy in an organized
way, the DOT groups jobs into “occupations” based on their similarities and
defines the structure and content of all listed occupations. Occupational
definitions are the result of comprehensive studies of how similar jobs are
performed in establishments all over the nation and are composites of data
collected from diverse sources. The term “occupation,” as used in the DOT,
refers to this collective description of a number of individual jobs performed,
with minor variations, in many establishments.
The process of arriving at the 12,099 occupations defined in the fourth
edition involves two steps, which are described in detail in chapters 6 and 7.
First, on the basis of actual observation of workers in a number of positions, a
job description is written by completion of a job analysis schedule. Then the job
descriptions are grouped into occupations, and composite descriptions are
prepared for inclusion in the DOT. Conceptually, these two steps are similar;
both “job” and “occupation” are theoretical entities. The central question in
creating these entities is how to delineate the boundaries, by deciding how
much heterogeneity should be tolerated within them.
The same kind of question arises in the next step in the process: arranging
the 12,099 occupational definitions into a classification structure. The
remainder of this chapter is devoted to this topic.
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GROUPING OCCUPATIONS
Traditionally, the Employment Service has used the occupational titles in
the DOT in a relatively straightforward manner to match available jobs and
workers. For example, those who indicate that they are plumbers (or have
worked as plumbers) are matched with any openings for plumbers on file at the
local Employment Service office. The matching procedures are relatively
uncomplicated if there are job openings for plumbers (and if the plumber is
satisfied with one or more of the available positions).
A more difficult question arises when there are no openings in the
occupation in which a worker is classified. In such instances the Employment
Service either must send the worker away without offering him or her any
opportunity for employment or must make fundamental decisions about the
similarity of occupations and accurate estimates about the degree of
transferability of the worker's skills and experience in past occupations to one or
more alternative occupations. Interviewers apparently do this quite frequently.
As we have already noted, assessing the transferability of skills goes beyond the
paradigm for job-worker matching that originally motivated the DOT and was
expressed in its first edition; the underlying principle is, however, extremely
important.
Workers typically can perform in many occupations besides the ones in
which they have previously been employed; moreover, many skills are learned
on the job. It may be that for a large number of jobs, previous work experience
is more or less irrelevant. Among the 12,099 occupations described in the DOT
we find a great many that appear to involve similar skills and aptitudes. For
example, workers who have experience as a Landscape Laborer (408.687–014)
may be reasonable referrals for occupations such as Laborer, Brush Clearing
(459.687–010) and Laborer, Golf Course (406.683–010). We note, however,
that these occupations are not grouped together in the DOT's classification scheme.
Since the DOT classification is used to organize files of job openings and
applicants in local Employment Service office job banks, the location of
occupations in the classification structure will effectively determine to which
job openings a job seeker is exposed. This is particularly the case if the lists of
job openings are extensive, as they are in large labor markets. The Landscape
Laborer (408.687–014) mentioned above might have to search through listings
for many jobs before coming upon an opening for a Laborer, Brush Clearing
(459.687–010). To the extent that any ordering scheme makes it easier to locate
an appropriate job, it obviously increases the employment opportunities of
workers, especially since (in the offices we visted) more than 70 percent of all
Employment Service job referrals
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are made by workers themselves finding appropriate job openings in the lists
maintained by the employment office.
It is simple to observe that a system that directs landscape laborers only to
openings in that field and does not refer them to employment opportunities in
related areas is overly restrictive. It is a far less simple matter to develop a
general solution to this problem. The difficult question is how to decide, in
general, what constitute reasonable occupational referrals. How does one decide
what occupations are similar? How can one expand the employment
opportunities of workers who seek work at the local Employment Service offices?
Two plausible approaches to these questions are embodied in the
classification structure of the fourth edition DOT. First, occupations are
organized in groups essentially according to technologies; 559 of these
occupational groups are represented by the first three digits of the DOT
occupational code. Second, each occupation is also characterized by the
requirements it places on workers in terms of their interaction with data, people,
and things; these requirements are represented by the second three digits of the
code. Either set (or both sets together) of digits could be viewed as a reasonable
index of the similarity of occupations, although it is important to note that
neither has ever been validated against an external standard. In the fourth
edition the occupational titles and their definitions appear in order according to
the numerical DOT codes. This ordering means that the technologically defined
groups have precedence in the classification system over the worker function
groups.
The DOT Code: The First Three Digits
The occupational groups represented by the first three digits of the code
appear to have been developed in an ad hoc manner—by considering a
composite of industry; work field; machines, tools, equipment, and work aids
(MTEWA);1 and materials, products, subject matter, and services (MPSMS). (See
chapter 6 and U.S. Department of Labor (1972:5–7) for a detailed discussion of
these concepts.) In assigning the first three digits to an occupation, the job
analyst or the definition writer is instructed to consult the DOT's existing
classification, particularly the narrative descriptions of the major categories and
divisions, in order to identify in which of the 559 occupational groups the
occupation belongs. This process involves
1In the work field “logging,” for example, the following descriptions of tasks are
suggested: “Climbs tree, using climbing spurs and safety rope, and cuts limbs, knots, and
top from tree with ax and handsaw” (U.S. Department of Labor, 1972:89).
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a good deal of judgment, since some of the categories are very similar. In the
absence of more specific guidelines, the DOT code may be assigned in a
somewhat arbitrary manner. Moreover, reliance on the existing classification of
the third edition DOT as the bench mark for the assignment of category codes in
the fourth edition undoubtedly discouraged rearrangements of the classification
and changes in codes. While definition writers for the fourth edition could in
principle recommend that categories be combined or eliminated or that new
ones be created, there is no documentation of such recommendations.
The DOT Code: The Second Three Digits
The third edition DOT and various trial matching programs used the worker
function scales (the second three digits of the DOT code) to identify occupational
groups,2 but the fourth edition makes no attempt to do so. Attempts to classify
occupations solely on the basis of their complexity in relation to data, people,
and things have been generally unsuccessful. An automated matching system
based on worker function codes did not work out, nor did a manual matching
attempt in Pittsburgh during the experimental period prior to publication of the
third edition.3
Despite the failure of the worker function scales to serve as an adequate
basis for matching, the concept is probably useful in developing a classification
system for matching. The worker functions are intended to summarize
characteristics of workers required by the job (such as their interests and
aptitudes).4 They were developed from a realization that every job is actually a
job-worker situation and that to describe such a situation adequately, knowledge
of the characteristics of both the job and the worker is required. The worker
traits required by a job are not
2The 22 major categories of the worker function scales, called areas of work, appear to
have been developed in an ad hoc manner. Within each category, occupational groups of
related worker function codes are created, but the correspondence of groups to codes is
not unique. The same worker function code (e.g., .288) often appears in many different
groups. This is perhaps not surprising, since worker function codes attempt to measure
the complexity of the job and omit reference to specific skills, which are often important
in placement.
3Interview, Adaline Padgett, occupational analyst, Division of Occupational Analysis,
U.S. Employment Service, August 1979.
4In their description of the Functional Occupational Classification Project, Fine and
Heinz (1958) recount the process by which all the occupational measures created for a
group of 4,000 experimental occupations were used as bases for sorting the data into
groups of similar occupations; they concluded that the worker functions form the best
groups because the profile of the occupations on all the other variables was fairly
consistent within worker function groups, at least more so than for groups formed on
other bases. It should be pointed out that the techniques for discerning common patterns
in data have advanced significantly since the mid-1950s when this research was done.
Fine and Heinz sorted the data repeatedly in a search for consistent patterns.
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captured by the considerations that currently enter into determining the first
three digits of the DOT codes, which appear to be based primarily on
technological processes.
Summary
Because the transferability of skills is generally regarded as the most
appropriate criterion for assessing the similarity of occupations with a view to
matching jobs and workers, the two aspects of the classification structure
inherent in the DOT codes (the first and second sets of three digits) were
ostensibly designed to capture two important elements of the transferability of
skills. The first element is job-specific knowledge or skills—the technological
aspects of the occupation, the particular subject matter, and the materials and
equipment used. These are described by the first three digits of the DOT code.
The second element involves the qualities of workers that are required by jobs.
These are thought to be captured by the worker function codes (the second three
digits) because the worker function configurations “profile” a variety of worker
traits consistently. These two bases of classification of the occupational titles in
the DOT are conceptually quite appropriate in the judgment of the committee.
The implementation of these concepts in practice, however, appears to be
somewhat inadequate, and it remains an open question whether these two
elements of the transferability of skills could not be better tapped by indicators
based on other methodologies.
THE KEYWORD SYSTEM OF THE EMPLOYMENT
SERVICE
More an alternative mechanism for matching job applicants with job
openings than an alternative classification system, an automated keyword
system has been implemented in a number of Employment Service offices
throughout the country. This system was the subject of a limited staff review,
reported in Appendix G. The main conclusion that should be drawn from this
review is that although automation of the matching process is highly desirable,
the keyword system as it is currently implemented suffers severe difficulties
and needs to be thoroughly reviewed by a committee of experts, a task that goes
beyond the charge to our committee.
EXISTING ALTERNATIVE CLASSIFICATIONS FOR JOB-
WORKER MATCHING
Several alternative methodologies for constructing occupational
classifications have been developed in recent years. The task inventories and
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the Position Analysis Questionnaire (PAQ) techniques described below may be
especially useful in identifying the types of skill components involved in
particular tasks and jobs. The identification, measurement, and classification of
skills is at the heart of the problem of person-job matching. With a thorough
understanding of the skills required by a broad variety of jobs as well as sound
measures of those skills, it might be possible to develop taxonomies of persons
and occupations that would facilitate differential placement, counseling,
guidance, and education (see Altman, 1976; Canada Employment and
Immigration Commission, Occupational and Career Analysis and Development
Branch, 1978; McKinlay, 1976). The feasibility of developing classifications
based on knowledge of skill content, at least in certain fields of work, is
illustrated by descriptions of certain military occupations (Morsh, 1966). The
PAQ data for 746 jobs have been used to create job families based on worker-
oriented dimensions of skill, omitting the technological aspects (Shaw et al.
(1977); also see Colbert and Taylor (1978), Taylor (1978), and Taylor and
Colbert (1978)). Another inventory, the Occupational Analysis Inventory, has
been used to group 1,414 jobs into 21 clusters (Pass and Cunningham, 1976).
Classifications based on job dimensions derived from structured job
analysis or task inventories, when combined with taxonomies of human
performance (Fleishman, 1975), appear to provide another way to address
directly the issue of the suitability of workers' skills, abilities, or other
characteristics for specific categories of jobs. As Dunnette (1976:516) notes,
there now exist several methods for describing or predicting how efficiently
different persons may be expected to perform various work functions:
Further research…should focus on developing…short, easily administered,
and easily understood behavior description inventor[ies] which may be used as
a common basis for classifying jobs, tasks, job dimensions, human attributes,
aptitudes, skills, and tests and inventories into the same taxonomic system.
Because of the level of detail involved in inventory approaches, research
has been limited so far to a few work areas. Many more areas would have to be
studied to make these techniques generally useful in developing classifications
for person-job matching purposes. Despite this limitation the inventory
approach is one that appears to be worth pursuing.
Counseling psychologists have attempted to create classifications of
workers and jobs of the sort suggested by Dunnette. The resulting systems for
person-job matching do not involve as much detail as do the task inventory
approaches and are also more indirect, usually relying on the characteristics of
persons rather than the characteristics of the work itself for the development of
the matching scheme. Two attempts, the
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Minnesota theory of work adjustment (Borgen et al., 1972; Dawis and Lofquist,
1974, 1975, 1976; Lofquist and Dawis, 1969; Rosen et al., 1972) and Holland's
theory of careers (Holland, 1966, 1968, 1973a, 1976; J. Holland and
G.Gottfredson, 1976; Holland et al., 1972) use classifications of occupations to
explain vocational adjustment and vocational choice, respectively. These two
schemes are of interest for three reasons: First, both theories have developed
occupational classifications for the specific purpose of matching workers with
jobs. Second, both theories incorporate independent but parallel classifications
(Holland) or characteristics (Minnesota) of persons and occupations and explicit
procedures for specifying the degree of match between a person and a number
of occupations. Third, both perspectives have generated substantial research.5
MINNESOTA THEORY OF WORK ADJUSTMENT
According to the Minnesota theory, the greater the correspondence
between a person's abilities and the patterns of aptitudes required by a job, the
better his or her performance (satisfactoriness) and the greater his or her
persistence in the job. Similarly, correspondence between a person's “needs”
(values, interests) and patterns of occupational reinforcers leads, according to
the theory, to job satisfaction and persistence. Recently, Dawis and Lofquist
(1974, 1975) have also used occupational aptitude pattern clusters and
occupational reinforcer pattern clusters to form a classification of occupations
and have shown how this classification is related to the DOT and Holland
classifications.
In general, the evidence about the usefulness of the Minnesota theory
implies moderate support for the theory and its associated tools (Betz et al.,
1966; Elizur and Teiner, 1977; Weiss et al., 1965, 1966). The theory predicts
satisfaction more efficiently than performance, and researchers have found
relatively stable differences among occupations in their patterns of reinforcers
and aptitude requirements. It is also clear that predictions of performance
(satisfactoriness, satisfaction, and persistence) are relatively inefficient, even
with the aid of this elaborate and carefully constructed set of tools for person-
job matching. These relatively weak predictions of important job-related criteria
are not, however, limited to this particular theory. In this area of research,
strong statistical associations between predictors and criteria are rare (Dunnette,
1976; Ghiselli, 1973; Schletzer, 1966).
5For reviews, summaries, critiques, and important tests, see Osipow (1973), Walsh
(1973), McCormick (1979), McKinlay (1976), L.Gottfredson (1978), and Rounds et al.
(1978).
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The major limitations of the Minnesota theory are twofold. First, it relies
on a number of indirect approaches to the determination of job characteristics,
inferring them, for example, from employee or supervisor ratings or from the
characteristics (especially abilities) of workers who are employed in an
occupation. Second, the range of occupations for which occupational
reinforcers and aptitude patterns are available is currently limited; data for only
148 occupations are available. Nevertheless, the Minnesota work demonstrates
that, in principle, it is possible to engineer the independent assessment of
persons and jobs in parallel ways so that the degree of worker-job match can be
estimated. Such an approach could prove effective in capturing the two
elements of skill transferability noted above, particularly the qualities of
workers that are required by jobs.
HOLLAND CLASSIFICATION OF CAREERS
The second counseling approach to person-job matching is illustrated by
Holland's (1973a) theory of careers. Holland has developed a typology of
persons and occupations that includes six types: realistic, investigative, artistic,
social, enterprising, and conventional. Inventories such as the Vocational
Preference Inventory (Holland, 1978), the Self-Directed Search (Holland,
1973b), the Strong-Campbell Interest Inventory (Campbell, 1977), or
l'Inventoire Personnel (DuPont, 1979) are used to locate individuals in this
typology, and, in turn, the modal characteristic of incumbents in a particular
occupation is used to characterize that occupation.6 For counseling purposes,
matches are made between the personalities of individuals and this
characterization of occupations. Underlying the Holland classification is the
notion that vocational choices are expressions of personality; thus there should
be greater similarity between the personalities of incumbents of the same
occupation than between incumbents of different occupations. Person-job
congruence is said to exist when the personality type that a person most
resembles accords with the category into which a given occupation falls.
Congruence leads, according to the theory, to satisfaction, success, and stability
or tenure in an occupation.
6Often, when data on profiles of job incumbents are unavailable, Holland and his
colleagues resort to indirect approximations involving a substantial degree of judgment
in classifying occupations. Use has been made of Strong Vocational Interest Blank data,
Kuder Preference Inventory data, PAQ data, and observations of regularities between the
Holland occupational classification and the DOT classification (Holland, 1973a; Holland
et al., 1972). Approximation techniques exist for assigning a Holland category to all
1960 and 1970 census occupations (L.Gottfredson and V.Brown, 1978) and to all third
edition DOT titles (Viernstein, 1972).
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Tests of Holland's theoretical formulations have had mixed results. On one
hand, despite the amount of subjective judgment involved in the classification
of occupations, the occupational classification shows strong relationships of
expected kinds with the Minnesota occupational reinforcer scales; the DOT
worker functions, SVP, and GED ratings; self-direction; and prestige
(L.Gottfredson, 1978; Rounds et al., 1978). The Holland occupational
classification has also been shown to be efficient in organizing occupational
mobility data in that the category of a worker's later job is substantially
predictable from knowledge of the category of a worker's earlier job for those
who change jobs (G.Gottfredson, 1977; Holland et al., 1973; Nafziger et al.,
1974). Finally, evidence verifying the dimensions of vocational interests that
underlie Holland's classification of persons implies that his groupings are
reasonably sound (Guilford et al., 1954; Hanson and Cole, 1973; Nafziger and
Helms, 1974).
On the other hand, the classification appears to be most useful when it is
supplemented by a general measure of occupational level such as the GED. It
focuses primarily on occupational preferences, and the measurement of
occupations is indirect. The occupational classification resembles in some ways
the approach to development of the Occupational Ability Patterns of Dvorak
(1935) and Patterson and Darley (1936) during the depression, paying little
direct attention to the details of the work performed or the skills required to
perform them. Also, it organizes occupational mobility and congruence data
better for older than for younger people (G. Gottfredson, 1977; L.Gottfredson,
1979).7 Variation in the methods used to classify occupations or persons results
in slightly different classifications (“identifications” in Sokal's (1974) terms).
Moreover, Holland's theory is incomplete with respect to the roles played
by social class, intelligence, and special aptitudes in the allocation of persons to
jobs. The theory incorporates a number of secondary propositions about the
degree of congruence among the personality and occupational types that have
not been discussed here (see Holland, 1973a). In general, the research tests of
these secondary propositions have yielded weak support (G.Gottfredson, 1977;
Nafziger et al., 1974; Rounds et al., 1978). The proposition that congruence
leads to success in an occupation is largely untested, and the evidence that
congruence leads to job satisfaction is very weak (see the studies cited by
Rounds et al. (1978)).
7Perhaps this reflects the fact that individual traits change over time as a result of
occupational experience, in such a way as to create greater conformity between
individual and occupational characteristics (Kohn and Schooler, 1973).
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SUMMARY
In short, the Holland and Minnesota approaches to person-job matching
illustrate the value of independent but parallel assessments of persons and jobs
and of the resulting occupational classifications, but both approaches employ
limited mechanisms for the assessment of actual job content and skill
requirements. An approach to occupational classification that seeks a middle
ground between the extreme specificity of task analysis and the detailed
examination of human abilities exemplified by Fleishman's (1975) work, on one
hand, and the more global but indirect approaches to the parallel classification
of persons and jobs illustrated by the Holland and Minnesota schemes, on the
other, may be a fruitful approach to the improvement of the classification of
occupations for the purpose of matching workers and jobs.
A MOBILITY-BASED APPROACH TO JOB-WORKER
MATCHING
The transferability of skills between occupations should be the primary
basis for classifications whose purpose is job-worker matching. The mobility
that occurs in the labor market, specifically the changes between occupations
that workers sometimes make when they change jobs, provides one indicator of
the transferability of skills between occupations. If workers move frequently
back and forth between a pair of occupations, we can infer that the occupations
require similar aptitudes and skills, or at least that those who perform one
occupation are generally capable of performing the other; otherwise, transfers
would not occur.8 Classifications that have been developed for the purpose of
job-worker matching should group together those occupations among which
workers commonly transfer. As we have seen, in the DOT classification many
jobs that appear to require similar skills are placed in widely different
occupational categories. For example, Dispatcher, Radio (379.362–010) is
classified as a protective service occupation, while Dispatcher, Traffic or
System (919.162–010), which involves essentially the same skills, is classified
as a miscellaneous transportation occupation. Similarly, Engraver, Hand, Hard
Metals (704.381–026) is classified as a benchwork
8Obviously, one-way transfers must be treated more cautiously, since they may
represent promotion ladders. It would not be desirable, for example, to send an assembly
line worker to an opening for foreman even though foremen are almost entirely drawn
from the ranks of line workers. In practice, however, this is not much of a problem, since
supervisory personnel are almost always promoted from within. See Appendix H for a
discussion of ways to use unidirectional transfers to infer career ladders.
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occupation, while Die Maker (979.281–010), which involves similar tasks, is
classified as a miscellaneous occupation.
Naturally occuring mobility between occupational categories is a sufficient
but not necessary indicator of the transferability of skills. There are many jobs
between which mobility does not occur despite similarity in content, because of
custom, discrimination, or other reasons (McKinlay, 1976). For example,
women who are secretaries move into managerial jobs only rarely, primarily
because of tradition and prejudice, even though secretarial skills such as
planning and coordinating may be highly relevant to many managerial jobs.
Hence it would be unwise to rely on mobility patterns as the only or even the
primary basis for assessing occupational similarity.
However, a mobility approach may provide a useful supplement to
traditional methods of assessing the similarity of occupations and the
transferability of workers, by providing an empirical criterion for judging the
similarity of occupations and the substitutability of labor.9 Whereas the
classifications we have reviewed above rely mainly on analysts' judgments
regarding the similarity of jobs, in the mobility approach, occupations are
grouped solely because of high degrees of movement between them. The nature
of occupations need not be analyzed in order to identify similarities to be used
as a basis for classification; it is necessary only to locate movement among
occupations, whatever their nature. (The mobility approach must, however, rely
on other approaches to define the basic occupations; 100 million positions in the
economy must first be classified into a reasonable number of occupational titles
before movement between occupations can be assessed.) In this section we
describe the potential of mobility data as a basis for constructing classifications
and enumerate the advantages and disadvantages of this approach.
We have undertaken some exploratory analyses to assess the feasibility of
developing alternative classifications based on the available job mobility data.
Basically, we attempted to group in clusters those jobs between which the rates
of transfer were high. Technical details of these analyses are provided in
Appendix H; for similar work, see Dauffenbach (1973). Our analyses have led
us to several general conclusions:
1. Mobility data can be useful for constructing an occupational classification
that is useful for placement, but the basic occupational titles for which
mobility data are collected must be defined by other procedures.
Occupational mobility data can contribute little to the definition of
9See Roe et al. (1966) and Holland et al. (1973) for earlier studies of classifications
using mobility data.
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occupations as clusters of similar jobs. For this work other methodologies
such as job analysis or task analysis are required.
2. Some plausible statistical models for transfers are available and can be used
as a guide in evaluating and generating classifications and career ladder
orderings.
3. It is technically feasible to construct occupational categories so that most
transfers take place within relatively small groups and according to career
ladders. Computations for developing such a classification might cost
several hundred thousand dollars if the full set of 12,099 DOT titles were
used. New algorithms would have to be developed.
4. It is technically feasible to apply this kind of analysis to the job history data
currently gathered from Employment Service clients, since these job
histories are routinely assigned DOT codes.10
5. Classifications based on observed transfers among occupations suggest
hypotheses about how the observed mobility has come about.
Independently generated data on task and skill similarities, and also on the
social characteristics of incumbents of occupations (e.g., age, sex, and
race), could be used in conjunction with data on mobility rates to further
our understanding of how people move among jobs.
6. Because some transfers may be excluded (or included) for reasons other
than those having to do with the transferability of skills, such
classifications should not be used uncritically. It is necessary to examine
the job content of the occupational categories suggested by the mobility-
based clusters in order to include any additional potential transitions and in
order to exclude absurd clusters created as artifacts of the statistical
algorithm.
ADVANTAGES AND DISADVANTAGES
The mobility approach to developing placement-oriented classifications
has several advantages. First, it can be developed from data already collected by
the Employment Service, which in its day-to-day operations routinely collects
work histories from applicants. For each local labor market and for the specific
clientele they deal with, the Employment Service collects all the data needed to
find out what occupational linkages commonly occur. Second, the mobility
approach allows for great flexibility and continuous improvement. Since the
underlying mobility matrices can be continuously updated by using data from
the ordinary operations of the Employment Service, classifications for matching
can be altered as labor
10To be useful, these data would have to be preserved as a nine-digit occupational
code. At present, the third through ninth digits are discarded when the interview data are
keypunched.
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market conditions change. For example, by using regularly updated transition
matrices for a local labor market, the procedure could reflect the fact that the
opening of a new automobile assembly plant had created new employment
opportunities for workers formerly employed as coal miners. Third, this method
avoids the ad hoc judgments of program designers, occupational analysts, or
vocational counselors in deciding what are similar and dissimilar occupations
for the purpose of job referral; it relies instead on the actual experiences of
workers as they test various alternatives in the labor market. Fourth, the
approach would overcome problems inherent in the overly narrow occupational
classifications of the DOT, since all occupations between which workers
routinely transfer would be grouped together.
The mobility approach, however, is not without its disadvantages. First, as
noted earlier, the resulting categories will reflect in part the current practices of
employers rather than the potential possibilities for transfer inherent in the
nature of transferable skills among occupations. Employers may perpetuate,
even unwittingly, discriminatory or stereotyped hiring practices, or they may
fail to perceive the potential of workers to move into new occupations. To the
extent that this occurs, the use of a classification based on actual transitions will
continue to perpetuate these undesirable limitations on workers' employment
opportunities. Second, and analogous to the first disadvantage, the resulting
classification will reflect in part the current preferences and possibly limited
horizons of job seekers themselves. Such a classification might not expose
workers to what has not been tried before. Third, if the resultant groupings are
based on data generated by Employment Service activity, they will reflect in
part the practices of the Employment Service itself. When workers with
particular occupational histories are referred most often to job openings in
certain other occupations on the basis of currently used classificatory practices,
these patterns in referral practices will naturally tend to appear also in data on
placements. Fourth, the reliance on job histories to provide mobility data may
result in classifications that meet the needs of new entrants and labor market
reentrants inadequately. Fifth, regularities in occupational transfers per se may
tell us little about the desirability of the transfers from the point of view of
either the employer or the employee. Placements may differ in terms of stability
or tenure of employment, productivity or performance, and employee
satisfaction or employer perceptions of satisfactoriness. Classifications based on
mobility data may group together, then, placements of differing usefulness;
such classifications do not provide information on the likely quality of the
matches, though labor market information (such as job tenure) could be used to
supplement the classification.
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STRATEGIES FOR IMPROVING OCCUPATIONAL
CLASSIFICATION FOR JOB-WORKER MATCHING
These disadvantages suggest that the mobility approach to developing
placement classifications must be supplemented by other information. First, and
most crucial, a reliable set of occupational definitions is necessary to provide
the data base for mobility studies. Job analyses, then, must continue to be the
basic building materials of classification systems. Second, because of current
limitations on labor market mobility, additional indicators of the transferability
of skills must be developed in order to encourage employers, workers, and the
Employment Service to try new types of matches. Again, job analysis
approaches are appropriate, as are vocational counseling approaches. Moreover,
mobility patterns might be studied to identify groups of occupations for which
specialized approaches such as task analysis would be particularly useful. Third,
because without supplemental information the mobility approach treats all
matches as being equally good, additional information about the quality of the
matches must be developed. There are two plausible approaches to developing
this information. The quality of the match could be inferred from labor market
data on, for example, the average job tenure of particular types of matches (e.g.,
coal miners in steel mills), or the quality of matches could be assessed by
directly querying workers and employers. Either approach could contribute to
improving the quality as well as the quantity of matches. Fourth, mobility data
must be supplemented by information about new entrants and returning
workers. Direct skill and ability assessment will continue to be useful in
developing placement possibilities, not only for those with limited labor market
experience but also for those workers who want to change careers.
OTHER METHODOLOGIES
Among the other alternative methodologies that may provide independent
assessments of occupational similarity, a prime candidate is task analysis
(including task inventories and position analysis questionnaires). Similar in
many respects to traditional job analysis, task analysis aims to describe
occupations in terms of the types of job tasks that are performed. It differs from
job analysis in both the explicitness of its attempt to assess the similarity of
occupations and its method of measurement. Task analysis has been extensively
used by the military services and to a lesser extent by other government
agencies such as the Public Health Service. By using data rating the extent to
which various jobs involve a common set of tasks, it is possible to apply
clustering and scaling procedures to construct a
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simplified description of the similarity of these jobs. The resultant description
may be used to construct a classification of jobs in which similarity is taken to
mean similarity in task content. This procedure could provide an alternative
perspective to the mobility approach to the similarity of occupations.
Worker characteristics can also be used to assess the similarity of
occupations. As we note above, classification systems developed by Holland in
his theory of careers or in the Minnesota theory of work adjustment tap
important dimensions of occupational similarity. Moreover, the techniques
developed by vocational counselors to assess the quality of matches from the
point of view of both workers and employers provide useful tools to assess the
success of various classification schemes in generating appropriate placements.
These techniques are also useful in providing knowledge of the skills, abilities,
and aptitudes of workers that supplement knowledge gained from job histories;
they will thus be particularly important for new entrants, reentrants, and those
wishing to explore different areas of work.
Classifications that are truly ideal for placement must make use of a
variety of approaches. Further research on developing classifications for job-
worker matching is particularly necessary along two lines. First, the use of
mobility data to indicate the transferability of skills and to locate plausible job-
worker matches should be investigated further. Second, methods for assessing
worker characteristics, such as skills, aptitudes, and interests, and indicators of
the adequacy of matches, such as satisfaction, performance, and persistence,
should be investigated.
A RESEARCH PROGRAM FOR DEVELOPING
CLASSIFICATIONS
A research program intended to develop or improve classifications for
placement purposes might evaluate several aspects of the resulting
classifications:
1. What heuristic value do the classifications have for contributing to an
understanding of the transferability of skills, barriers to labor market
mobility, or the segmentation or Balkanization of labor markets in both
desirable or undesirable ways?
2. How successful are the classifications in generating satisfactory
placements? What proportion of job referrals made using a classification or
matching scheme results in placements (i.e., employer decisions to hire and
applicant decisions to accept employment)? How long do the placements
last? Do persons referred to jobs continue working at those jobs for an
acceptably long period of time? Put another way, do alternative matching
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procedures make any difference for the employment stability of users of the
Employment Service?
3. What are the long-range outcomes of placements made in terms of the
income, job satisfaction, and performance of the persons placed?
4. How easy is it for employment interviewers, applicants, and employers to
understand and use each system?
5. Are different classifications useful for different aspects of job-worker
matching?
CONCLUSION
In this chapter we have reviewed the classification structure of the DOT as
well as alternative bases for systems of occupational classification and have
raised some of the conceptual issues involved in developing classifications for
job-worker matching, in particular the notion of occupational similarity and the
transferability of skills. We have suggested the use of data on naturally
occurring patterns of labor mobility to evaluate, refine, and develop new
occupational classifications.
Our analyses lead us to conclude that mobility-based methods may provide
a flexible methodology for evaluating and developing classification systems for
use in placement. They have the unique advantage of using the actual histories
of workers in the labor force as guides for defining what are appropriate (and
inappropriate) matches to make for individuals with a given occupational
background. This method avoids ad hoc judgments and permits greater
flexibility than previous centralized, once-a-decade exercises in occupational
grouping.
Nonetheless, our work also indicates a clear need for more traditional
occupational analysis procedures. At a minimum, such procedures are needed to
define the basic occupational titles. There are, however, other important reasons
for shunning excessive reliance on mobility data in making placement
decisions. Any history of occupational mobility reflects not only the potential
range of the transferability of workers' skills between various occupations but
also the patterns of discrimination in hiring and promotion that now exist (or
previously existed) in the labor market. So, for example, the fact that
administrative secretaries do not commonly advance into management
occupations may reflect patterns of sex discrimination in hiring and promotion
rather than any inherent lack of transferability of their skills. Any placement
system guided exclusively by the history of labor mobility between occupations
would build the past biases of the market into its future operations.
These considerations dictate that any mobility-based approach to
describing the similarity of occupations should be supplemented by other
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methods that do not depend on the past functioning of the labor market. An
independent perspective on the similarity of occupations is required. Traditional
occupational analysis procedures might play this role, although job analysis as
currently practiced in the occupational analysis program has not been especially
successful in defining the similarities of disparate occupations. In an approach
that emphasizes required worker characteristics, the most ambitious attack on
this problem has been the ratings measuring the complexity of a job in relation
to data, people, and things of the occupational analysis program's functional job
analysis approach. The validity of these ratings has not been studied
systematically, however, and their relationship to the potential transferability of
workers from one occupation to another remains to be shown. Moreover, as
chapter 7 indicates, the reliability of these measurements is questionable. Any
attempt to apply these particular measures as independent indicators of
occupational similarity should be grounded in future studies of their criterion-
related validity11 and ongoing quality control of their measurement.
Other alternative methodologies that should be explored are task analysis
or other forms of structured job analysis and person-job matches based on
vocational preference theories such as that of Holland. The integration of (1)
task analysis data obtained from representative samples of workers, (2) direct
observation of jobs using more traditional job analysis procedures and the
judgments of trained analysts, and (3) the assessment of workers' traits and
person-job matches using techniques developed by vocational counselors, with
(4) study of the naturally occurring patterns of labor mobility would provide a
more adequate basis for developing classification systems and operational
procedures for use by the Employment Service in matching jobs and workers.
11Criterion validity could be demonstrated by showing the relationship, if any,
between the ratings of occupations on DATA, PEOPLE, and THINGS variables and the ease
with which workers transfer between jobs in these occupations
Representative terms from entire chapter:
labor market
