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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>October</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Efectiveness of job title based embeddings on résumé to job ad recommendation</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Mesut Kaya</string-name>
          <email>mkaya@hum.aau.dk</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Toine Bogers</string-name>
          <email>toine@hum.aau.dk</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Aalborg University Copenhagen</institution>
          ,
          <addr-line>Copenhagen</addr-line>
          ,
          <country country="DK">Denmark</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2021</year>
      </pub-date>
      <volume>1</volume>
      <issue>2021</issue>
      <abstract>
        <p>For the task of job recommendations, common practice is to recommend job postings to job seekers, and recently diferent embedding techniques have been applied to solve this task. A common way to represent job seekers and job postings as embeddings is to use the whole textual data of the job postings and job seekers' resumes. Instead of using the whole textual data, textual data source like job title, knowledge, skills, abilities can be used as well. In this work, we present findings of a preliminary ofline study, where we explore the impact of utilizing diferent types of embeddings to recommend job seekers to given job postings, unlike the common practice of recommending job postings to job seekers. We explore the efectiveness of using job title based embeddings compared with the embeddings based on resume and job posting full-text descriptions. Using a dataset from JobIndex -Scandinavia's largest job portals and recruitment agencies- our experimental results show that representing job seekers and job postings as embeddings by using job title text only can be at least as informative as using the full-text descriptions for most of the cases.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>CCS CONCEPTS</title>
      <p>• Information systems → Recommender systems;
Personalization.
job recommendation, job matching, recruitment, embeddings,
erecruitment, HR</p>
    </sec>
    <sec id="sec-2">
      <title>INTRODUCTION</title>
      <p>
        The popularity of online job portals has broadened the potential
reach of both job seekers and companies with job vacancies by
enabling them to more easily make their resumes and job postings
available to each other in electronic form [
        <xref ref-type="bibr" rid="ref16 ref3 ref9">3, 9, 16</xref>
        ]. However,
assessing a larger number of available positions and candidate resumes
also places a greater burden on job seekers and recruiters [
        <xref ref-type="bibr" rid="ref16">16</xref>
        ]. Many
consider AI technology to have the potential to reduce this manual
burden, for instance, through the use of job recommender systems,
which attempt to automatically match job seekers with companies
with job vacancies [
        <xref ref-type="bibr" rid="ref16 ref9">9, 16</xref>
        ]. Recommending relevant jobs to a job
seekers or suggesting a list of relevant candidates for a job vacancy
is an important task of online job portals. Unlike item-to-people
recommendations, job recommendation is a reciprocal (or
peopleto-people) recommendation scenario [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ], in which both employer
and job seeker must be satisfied with the recommendations.
      </p>
      <p>
        Much of the recent research on job recommender systems has
focused on generating representations of both the job seekers’
resumes and and the job postings [
        <xref ref-type="bibr" rid="ref11 ref13 ref2 ref23 ref5">2, 5, 11, 13, 23</xref>
        ]. These embeddings
are then compared to each other to estimate how well a job seeker
matches a given job posting and vice versa. A common way of
representing job seekers and job postings as embeddings is by using
the whole textual content of resumes and job postings to train word
[
        <xref ref-type="bibr" rid="ref15">15</xref>
        ] or document embeddings [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ]—semantic representations of
each individual word or the document as a whole. Embedding words
or documents in the same semantic space is necessary, because
simple keyword matching between the entire text of job postings and
resumes can be problematic. Both are written by diferent parties
with diferent backgrounds, which can lead to a vocabulary gap [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ],
when the terminology used by job seekers to describe themselves
difers considerably from the text in the job postings.
      </p>
      <p>
        Embedddings can capture the semantic similarity between words,
phrases, sentences and potentially documents, and to a certain
extent, bridge the vocabulary gap between resumes and job postings.
Job recommendation approaches can vary in the data that they
use to represent both resumes and job postings in a shared latent
semantic space. While some researchers generate job
recommendations for job seekers using the knowledge, skills and abilities
extracted from resumes and job postings [
        <xref ref-type="bibr" rid="ref13 ref19">13, 19</xref>
        ], others have
computed resume embeddings using their historical interactions with
job postings. First, job postings are represented as embeddings,
after which job seekers’ embeddings are based on the embeddings
of job postings that they have previously interacted with [
        <xref ref-type="bibr" rid="ref10 ref11 ref5">5, 10, 11</xref>
        ].
      </p>
      <p>
        One of the most common data fields present in both resumes
and job postings is information about past job titles and current
job titles targeted in the job postings. According to Bernard et al.
[
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], recruiters match job seekers with job postings by considering
the past work experience and desired future opportunities of job
seekers. With some experience, recruiters can carry out this task by
only considering job titles without the need for going through the
entire textual description. Zhang et al. [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ] also states that proper
job title information can potentially provide guidance for both job
seekers and recruiters.
      </p>
      <p>
        In this work, we compare embeddings based solely on job titles
to embeddings of the entire textual description of resumes and job
postings. While the scenario of recommending relevant jobs to job
seekers is more common in the literature, in this paper we focus on
the inverse: recommending relevant candidates for a job, in efect
supporting recruitment professionals in their work [
        <xref ref-type="bibr" rid="ref20 ref7">7, 20</xref>
        ]. Our
work is part of a project to improve the matching algorithms used
by one of Scandinavia’s largest job portals, JobIndex1 located in
Denmark. Our data is in both Danish and English and originates
      </p>
      <sec id="sec-2-1">
        <title>1https://www.jobindex.dk</title>
        <p>
          with this company. In addition to exploring the value of job title
embeddings, we also explore the efect of using a location filter,
since job seekers tend to prefer jobs that are within reasonable
commuting distance from their home, just as companies prefer that
their future employees live within reasonable distance from the
company [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ]. Finally, we also compare the performance of using
pre-trained embedding models (e.g., word2vec model trained on
wiki data) with models trained on the Danish/English resumes and
job data.
        </p>
        <p>We find that using job titles only to represent job seekers and job
postings as embeddings mostly results in better recommendations
compared with embeddings based on the entire texts. For word2vec
models, experimental results show that training job domain-specific
embedding models improved the performances of recommendation
models that use pre-trained word2vec models. We also find that
using a location filter always improves the recommendation models’
performance.</p>
        <p>The remainder of the paper is structured as follows. In Section 2,
we review relevant research on using embeddings for the job
recommendation. In Section 3, we present our approach to the problem.
We describe our methodology, dataset and evaluation metrics used
for the experiments in Section 4. Experimental results are presented
and discussed in Section 5. Finally, we conclude in Section 6 with a
discussion of our findings and ideas for future work.
2</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>RELATED WORK</title>
      <p>
        Most of the early work on job recommendation has focused on
content-based filtering, collaborative filtering or hybrid
combinations thereof [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. More recent research in the area of job
recommendations involves representing job seekers and job postings as
embeddings in a latent space [
        <xref ref-type="bibr" rid="ref11 ref13 ref2 ref23 ref5">2, 5, 11, 13, 23</xref>
        ]. It is common to
represent both job seekers’ resumes and companies’ job postings on a
shared latent space by extracting shared skill sets, competencies,
occupation data [
        <xref ref-type="bibr" rid="ref13 ref19">13, 19</xref>
        ]. Alternatively, job seekers’ embeddings are
computed from their historical interaction data with job postings
where job postings are first represented as embeddings, after which
embeddings of job seekers are generated by using the embeddings
of job postings that they have previously interacted with [
        <xref ref-type="bibr" rid="ref10 ref11 ref5">5, 10, 11</xref>
        ].
      </p>
      <p>
        Unlike the common practice to recommend job postings to job
seekers, in this paper we focus on the problem setting of
recommending candidate job seekers for job postings. This problem is
also referred as talent search [
        <xref ref-type="bibr" rid="ref20 ref7">7, 20</xref>
        ]. Ramanath et al. [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ] present
their findings about using representation learning for talent search
at LinkedIn. Unlike our approach, they do not use textual data to
learn the embeddings but they represent categorical entities (e.g.,
skill, title, company) as embeddings by using a variety of graph
embedding algorithms.
      </p>
      <p>
        As we motivated in the previous section, job titles make up a data
type available in both job seekers’ resumes and job postings. Job
title information has been used as one of the important features for
the task of matching resumes and job posting [
        <xref ref-type="bibr" rid="ref14 ref18">14, 18</xref>
        ]. Our focus in
this paper is to examine the benefits of embedding resumes and job
postings using job titles alone. To the best of our knowledge, the
only work that uses embeddings of only job titles is the work by
Elsafty et al. [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Unlike our approach, they recommend job postings
to job seekers and they only create the representations of the job
postings using the embedding of (1) job titles, (2) full-text only and
(3) job titles and full-text combined. These three embeddings result
in recommendations for similar jobs. Our recommendation scenario
is inverted, in that we attempt to support recruitment professionals
by recommending job seekers in relation to a specific job posting. In
addition, we generate job title-based embeddings of both resumes
and job postings and recommend relevant candidates based on the
similarity of their resume embeddings to the job posting embedding.
      </p>
      <p>
        Liu et al. uses job title information together with skills and
location information. They parse resumes of job seekers and job
postings to extract job titles, skills and location information. Then,
they build job–job, skill–skill, and job–skill graphs from historical
data to learn a joint representation for both job titles and skills by
encoding the local neighborhood structures captured by the three
graphs [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
3
      </p>
    </sec>
    <sec id="sec-4">
      <title>OUR APPROACH</title>
      <p>
        Previous work has shown that learning embeddings on textual
description of job postings can improve the accuracy of
contentbased recommendations [
        <xref ref-type="bibr" rid="ref10 ref11">10, 11</xref>
        ]. We also try to use diferent textual
data from the resumes of job seekers and job postings (see Section
4.4) to create their embeddings and create recommenders that use
those embeddings.
      </p>
      <p>We denote the set of users as U and set of items as I. In our
problem setting, we consider recommending job seekers to given
job postings, we define a job posting as a user  ∈ U and a job
seeker as an item  ∈ I. Given a textual data source that consists
of a sequence of tokens  = {1, 2, . . . ,  }, by using a pre-trained
embedding model (we explain diferent type of embedding
models used later in Section 4.3), we represent  as a -dimensional
vector ®. For simplicity, we refer to user vectors as ® , and item
vectors as ® . We also represent the interaction history of a user
 as ℎ = {®1, ®2, . . . , ® } by considering the vector
representations of all items that the user has positively interacted with,
and similarly we represent the interaction history of an item  as
ℎ = {®1, ®2, . . . , ® } by considering the vector representations
of all users that has positively interacted with the item . The
recommendation task is then—given a ‘reference’ vector ® that is
the representation of a user  (i.e., job postings)—to find the top- 
similar vectors among item vectors (i.e., job seekers).
3.1</p>
    </sec>
    <sec id="sec-5">
      <title>Recommendation Models</title>
      <p>
        To obtain the final vector representation of users ® (job postings)
and items ® (job seekers) and to perform the recommendation task,
we define the following models:
• EMB: Job seekers’ representations are based on textual data
from their resumes while job postings’ representations are
based on the textual data from the job postings. In other
words, given a user  with its textual data  = {1, 2, . . . ,  },
® is computed by using  and any given embedding model.
Similarly, for a given item  its vector representation is
computed by using  and any given embedding model. This
variant can be used for cold-start scenario since it does not
require any interaction data between job seekers and job
postings.
• EMBUH : This variant calculates embeddings based on the
user history (EMBUH). Given an item  and its textual data
 , ® is computed using  and any given embedding model.
After computing all item embeddings in I, for a given user
, its representation is the average of the item embeddings in
ℎ (i.e., a job posting’s embedding is the average2 of all the
resumes’ embedding vectors that had a positive interaction
with the job ad).
• EMBUHL: This variant is similar to EMBUH, but is limited
to using only the latest user history (EMBUHL). The only
diference is, instead of considering all items in ℎ , we only
consider the embedding of the item that has the latest
interaction with the user . This variant is similar to the previous
work that considers the recency of the interactions [
        <xref ref-type="bibr" rid="ref10 ref11">10, 11</xref>
        ].
• EMBIH : This variant calculates embeddings based on the
item history (EMBIH). Given a user  and its textual data  ,
® is computed using  and any given embedding model.
After computing all user embeddings in U, for a given item
, its representation is the average of the user embeddings in
ℎ (i.e., a job seeker’s embedding is the average of all the job
postings’ embedding vectors that it had a postive interaction
with).
• EMBIHL: This variant is similar to EMBIH, but uses only
the latest user history (EMBIHL). The diference is, we only
consider the embeddding of the user that has the most recent
interaction with the item.
3.2
      </p>
    </sec>
    <sec id="sec-6">
      <title>Location filter</title>
      <p>As we will explain in more detail in Section 4.1, both job postings
and resumes come with a set of geo-location identifiers. We denote
the set of location IDs that a job seeker  is interested in as  .
Similarly, we denote the set of location IDs that is provided in a job
posting  as  . To apply location filter to any of the
recommendation models explained above, we simply take the intersection of 
and  . Then, for a given user , we filter out all candidate items
where the resume and job posting location IDs are disjoint sets, i.e.,
where the intersection is empty.
4</p>
    </sec>
    <sec id="sec-7">
      <title>METHODOLOGY</title>
      <p>In this section, we explain the details of our ofline evaluation
methodology, by describing our dataset, the diferent embedding
models we tested in our experiments and the textual data used
to created the embeddings, as well as the baseline recommender
algorithms we compared them against.
4.1</p>
    </sec>
    <sec id="sec-8">
      <title>Dataset</title>
      <p>We extract our data from the data dump provided by JobIndex. The
dataset contains both job postings and anonymized resumes in a
semi-structured textual format. While most resumes and job
postings are in Danish (89.45% of resumes and 81.95% of job postings),
a small portion are in English (10.55% of resumes and 18.05% of job
postings).
2A comparison with other methods for combining item embeddings into a single user
embedding vector is left as future work.
4.1.1 Metadata. Each job posting contains a textual description
of the job in question, an appetizer text that summarizes the job
posting, the job title of the job posting and a list of of location
IDs corresponding to the location of the company ofering the
position. Each resume contains a resume text in which job seekers
describe themselves, a list of job titles that they are interested in
or have previous work experience in, and a list of location IDs
corresponding to the geographic area(s) they prefer to work in.
4.1.2 Interaction Data. The dataset also contains data on
interactions between job seekers and job postings. When recruiters
associated with the job portal identify job seekers as relevant
candidates for a job, they can contact them by sending them a message
containing a short introduction, argumentation for why they should
apply for the job, and an embedding version of the job posting. In
addition, each contact email has a link that makes it easy for job
seekers to provide feedback on the recommendation. Job seekers
can respond to the recruiters either positively or negatively. Our
dataset contains 268,442 resumes and 426,226 job postings. On
average, 18.4 job seekers are contacted per job posting. Out of those,
10.9 job seekers do not respond, 5.1 of them respond negatively,
and only 2.4 of them respond positively. In this work, we consider
positive interactions only and we filter out the negative responses 3.
In addition, we filter out all jobs with less than 5 positive responses
to make sure that each user has at least one item in validation and
test set (see the following section for more details). Our final dataset
contains 98,172 resumes and 45,173 job postings. It contains a total
of 303,758 positive interactions with an average of 6.7 user actions
(users are job postings) and 3.1 item actions (items are job seekers).
The sparsity of the dataset is 99.99%.
4.1.3 Dataset Splits. After pre-processing the dataset, we partition
the interactions into training, validation and test sets such that 60%
of each user’s interactions are in the training set, 20% of them are in
the validation set and 20% are in the test set. We use the timestamp
information to keep the most recent interactions in the test set.
Note that, since we use positive interactions only, all items in the
test set are considered as relevant items in the experiments.
4.2</p>
    </sec>
    <sec id="sec-9">
      <title>Baselines</title>
      <p>
        As our two baseline algorithms— following [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]— we use
itembased KNN (ItemKNN) [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ] together with a popularity-based
recommender (Pop) algorithms on the interaction data. We also tried
BPR [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ] and NeuMF [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ], but optimizing their hyperparameters
was not feasible due to time constraints.
      </p>
      <p>We use the Python library RecBole4 to run our experiments. It
has a hyper-parameter optimization module as well. For ItemKNN,
we optimize the number of nearest-neigbors parameter  using
the validation set. The value that optimized the MRR metric (See
Section 4.5) on the validation sets was  = 500.
3We leave the exploration of negative response data as future work, because there are
three diferent types of negative responses: (1) a job seeker is not interested in the job,
(2) they are not interested in working for that specific company, or (3) they have found
a job elsewhere. The latter is not necessarily a negative response as the job seeker may
still find the job relevant for them.
4https://github.com/RUCAIBox/RecBole
4.3</p>
    </sec>
    <sec id="sec-10">
      <title>Embedding Models</title>
      <p>
        We use publicly available pre-trained models as well as train our
own embedding models on the textual data of the resumes and job
postings in our dataset.
4.3.1 Pre-trained word2vec embeddings. We use a 100-dimensional
word2vec skipgram model [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ] trained on the Danish CoNLL17
corpus5.
4.3.2 Self-trained domain-specific word2vec embeddings. We also
train our own word2vec model using the Gensim6 library on the
resume text from the resumes and appetizer text from the job
postings. Similar to the CoNLL17-based word2vec model, we set the
embedding size to 100 and window size to 10.
4.3.3 Self-trained domain-specific doc2vec embeddings. Similar to
our self-trained domain-specific word2vec embeddings trained on
our dataset, we also train a doc2vec model on this data. Again, we
set the embedding size to 100 and we use Gensim’s implementation
of doc2vec. For word2vec-based models, a document ’s embedding
® is computed by taking the average of the each token’s  ∈  word
embedding. For doc2vec,  is computed by taking it as a document
and the model returns a single document embedding vector ®.
4.4
      </p>
    </sec>
    <sec id="sec-11">
      <title>Textual data used for embeddings</title>
      <p>Now, we will explain diferent ways (in terms of the textual data
used) to represent users and items as embedding vectors.
4.4.1 Embeddings of job titles. Resumes contain a field called job
titles that is a list of job titles the user aspires to or has held
previously. For job postings as well, there is the jobtitle field that
contains the job title of the position in question. Most of these job
titles are in Danish, but some of them are in English. We use a
Python language detection package7 to detect the language of the
text, after which we translate the English text to Danish where
necessary using another Python package8. Then, using any of the
models explained in the previous section, job title textual data of
the resumes and job postings are represented as -dimensional
embedding vectors.
4.4.2 Embeddings of resume text and appetizer text. Resumes
contain a field called resume text where job seekers write a description
text about themselves. For the job postings as well there is an
appetizer text that summarizes the job description. Similar to the job
titles, we detect English text and translate it to Danish where
necessary. Both job seekers (based on their resumes) and job postings
are then represented as embedding vectors similar to how this was
done for job titles.
4.5</p>
    </sec>
    <sec id="sec-12">
      <title>Evaluation Metrics</title>
      <p>We use a set of metrics commonly used for evaluating recommender
systems to compare our diferent algorithms. We use their Recbole
implementation9.</p>
      <sec id="sec-12-1">
        <title>5http://vectors.nlpl.eu/repository/</title>
        <p>6https://pypi.org/project/gensim/
7https://pypi.org/project/langdetect/
8https://pypi.org/project/googletrans/
9For the formulation of the metrics considered in Recbole, please refer to https://
recbole.io/docs/recbole/recbole.evaluator.metrics.html
For a user :
• Recall measures the proportion of ’s relevant test set items
that are in the top- results.
• MRR measures whether  finds an item that is in ’s relevant
test set in the earlier ranks of the top- results.
• Normalized Discounted Cumulative Gain (nDCG)
measures the extent to which  finds ’s relevant test set items
in the earlier ranks of the top- results. Like MRR, nDCG
is sensitive to the rank of items. Unlike MRR, it takes into
account all of the items in the top- results that are in ’s
relevant test set items.</p>
        <p>The results reported in the following section are the
macroaveraged means of each metric, i.e., we first compute them for each
user  ∈ U, after which we take the mean over all users. Given
the dificulty of the task and the sparsity of the data, we report all
results at the top-100 cut-of in the following sections.
5</p>
      </sec>
    </sec>
    <sec id="sec-13">
      <title>RESULTS</title>
      <p>In this section, we report our empirical findings of extensive
experiments. Table 1 shows results for experiments that use location filter.
We do not show the results for the experiments without applying
location filter since for all cases applying location filter always
improves the performance of the recommendation models, as
described in more detail in Section 5.4. The top section of Table 1
shows the results for Pop and ItemKNN baselines, of which the
latter outperforms the former. The middle section of Table 1 shows
the results of embeddings of job titles only and the bottom section
shows the results for the embeddings based on the full-text
representations. Vertically, Table 1 shows the results of three diferent
types of embedding models—pre-trained vs. self-trained
domainspecific word2vec embeddings and self-trained domain-specific
doc2vec embeddings.</p>
      <p>
        Overall, we find that the ItemKNN baseline almost always
outperforms the embedding-based recommendation models. These
results are in line with previous work by Lacic et al. [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ], who
also used doc2vec-based embeddings. They found that a user-based
KNN algorithm outperformed a doc2vec approaches in terms of
accuracy. However, collaborative filtering algorithms perform worse
in cold-start scenarios without any interaction data, so our
experimental setup and data filtering protocol most likely benefits
the ItemKNN baseline. In a real-world scenario, recruitment
professionals are tasked with finding relevant candidates for a new
job posting, which is a classic example of a cold-start scenario.
We therefore believe that exploring and comparing the diferent
embedding-based models is still valuable.
5.1
      </p>
    </sec>
    <sec id="sec-14">
      <title>Impact of job title-based recommendation</title>
      <p>Except for EMBIH, embeddings computed based on job titles only
outperforms embeddings computed based on the full-text
representations. This supports our claim that representing both job seekers
and job postings using only job titles can be valuable to a certain
extent.
5.2</p>
    </sec>
    <sec id="sec-15">
      <title>Pretrained vs. domain-specific embeddings</title>
      <p>
        For word2vec based models, we observe that, as expected, training
our own word2vec embeddings on the textual data of job postings
and job seekers’ resume data improves recommendation
performance over generic pre-trained embeddings. The EMBIH model is
again the only exception to this, where the pre-trained word2vec
model slightly outperforms using trained word2vec model on the
job data.
over without applying the location filter) . These results are in line
with the claim that companies are more likely to prefer job
seekers that are within reasonable commute distance and similarly job
seekers are more likely to prefer jobs that are posted by companies
that are within reasonable commute distance [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ].
5.3
      </p>
    </sec>
    <sec id="sec-16">
      <title>Word- vs. document-level embeddings</title>
      <p>For the embeddings based on job titles only, using word2vec models
to represent job seekers and job postings as embeddings for all
cases performs better than using doc2vec models. Compared with
documents containing a lot of tokens (e.g., job posting description),
job titles tend to contain only a few tokens and can even consist of a
single token, such as “economist”. That is why doc2vec may not be
suitable for job title-based embeddings compared with word2vec.</p>
      <p>For the embeddings based on full-text data, for only EMBIH
using doc2vec models performs better than using word2vec models.
For all EMBIHL, EMBUH and EMBUHL using word2vec models
performs better than using doc2vec models. Compared with documents
containing only a few tokens (e.g., job titles), job posting or job
seeker description contain more tokens. One would expect to have
better results for using doc2vec models. However, for some cases
using word2vec models on textual data containing more tokens can
perform better than doc2vec models. We plan to investigate this
behaviour further in future work.
5.4</p>
    </sec>
    <sec id="sec-17">
      <title>Impact of location filter</title>
      <p>Although the results are not shown for the experiments without
applying the location filter, for all configurations and recommendation
models, applying location filter always increases the values of all
evaluation metrics (for most of the cases at least 50% improvement
5.5</p>
    </sec>
    <sec id="sec-18">
      <title>Impact of recency</title>
      <p>
        For all cases, EMBUHL and EMBIHL always perform worse than
EMBUH and EMBIH. In other words, using the recency of the
interactions is performing worse than considering all historical
interactions. These results are diferent than the previous work that
considers the efect of recency of the interactions [
        <xref ref-type="bibr" rid="ref10 ref11">10, 11</xref>
        ]
(similar to us, they also consider the latest interaction to model the
recency). We note that, unlike our problem setting of
recommending job seekers to job postings, they recommend job postings to job
seekers.
5.6
      </p>
    </sec>
    <sec id="sec-19">
      <title>Impact of embedding size</title>
      <p>To explore the efect of embedding dimension, we run experiments
by varying the embedding size of the word2vec and doc2vec models
from the set {50, 100, 200, 300, 400, 500}. We report the performance
of diferent recommenders using nDCG in the Fig. 1. Fig. 1a shows
the results for job title based embeddings, and Fig. 1b shows the
results for full-text based embeddings. For each of the
recommendation algorithms EMB, EMBUH and EMBIH, we show the results
for both w2vec and doc2vec based embeddings. Mostly, for both
cases all recommenders reach their peak point for the embedding
sizes of 100 or 200.
0.05
0.04
0.03
G
C
D
n
0.02</p>
    </sec>
    <sec id="sec-20">
      <title>Example recommendations</title>
      <p>Table 2 shows the top recommended job seeker for two diferent
job postings. The top part of the Table 2 shows the job title of the
two job postings. The bottom part of the table shows the job titles
of the top recommended job seeker (a list of job titles that the job
seeker is interested in or have previous work experience in) for 3
diferent recommendation models, i.e., EMB, EMBUH and EMBIH.
For both examples, we can see the efect of using embeddings in
terms of capturing the semantic similarity between job titles, e.g.,
”Head of HR“ and “HR Director”.</p>
      <p>One point of interest are the recommendations generated by the
EMBIH algorithm for the job posting describing an “IT Support
Analyst” position. Here, we see that the list of recommended job titles
include “Bank employee”, “IT employee” and “Finance employee”.
As we explained in Section 3.1, EMBIH calculates the embedding of
job seeker with job title “IT Support Analyst” based on the item
history, i.e., job postings that the job seeker had a positive interaction
with. When we analyze the job seeker’s historical interactions, we
can see that the job seeker was mostly interested in “IT” positions
of some banks.
6</p>
    </sec>
    <sec id="sec-21">
      <title>DISCUSSION &amp; CONCLUSIONS</title>
      <p>In this work, we explored the impact of embeddings for tackling the
problem of recommending job seekers to job postings. We did
extensive ofline evaluation to compare diferent recommender models
by using embeddings based on diferent type of textual data source.
Specifically, we focused on the efect of using job titles only in
comparison with using full-text descriptions of job postings and
resumes of job seekers. We find that generating embeddings by
using only job titles typically results in better recommendations
with respect to diferent evaluation metrics, as compared with
embeddings based on the full-text representations of job seekers and
job postings. Experimental results also show that using location
iflter always improves the recommendations.</p>
      <p>
        We note that this is a preliminary study to explore the efect of
job title based embeddings for the task of recommending relevant
candidates for an open job posting. There are some limitations of
our current work:
• Job titles vs. industry. Although job title is a valuable data
source, we note that we are aware of some of the limitations
related to it. First, job postings or job seekers’ resumes can
have meaningless titles or no title at all [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. Second, job title
data can be messy data since it can contain a lot of subjective
and non-standard naming conventions [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ]. Third, using
job title for recommending job seekers to job postings can
be problematic for some specific cases. Consider a job title
“Project Manager” for two diferent job postings, and let’s
assume that the industry information is diferent for the
two, e.g., one job posting is for IT and the other for Finance.
Without using the industry information, embeddings based
on job title only will have the same matching degree for a job
seeker with job title “Project Manager” from any industry
to this specific job postings. We are planning to use job title
based embeddings together with embeddings based on other
textual data source like industry from both job postings and
job seekers’ resumes in the future.
• Multilinguality. As we explain in Section 4.4, we translate
English text to Danish where necessary. If the quality of the
translation is poor, embeddings may not be representative
for the translated text for the semantic similarity. We leave
the efect of using multilingual embeddings as future work.
• Alternative embedding models. In this work, we
investigated word2vec and doc2vec models to represent job seekers
and job postings as embeddings. We leave the efect of using
BERT-based embeddings [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] as future work.
      </p>
    </sec>
    <sec id="sec-22">
      <title>ACKNOWLEDGEMENTS</title>
      <p>This research was supported by the Innovation Fund Denmark,
grant no. 0175-000005B.</p>
    </sec>
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</article>