Marketing in the Public Sector—Beneﬁts and Barriers: A Bibliometric Study from 1931 to 2020

: The global economy has brought economic and social changes that have led organizations to extend their vision beyond consumer and business markets. Particularly, in the marketing of public sector (MPS), the extant theoretical foundations require more comprehensive investigations not only into the main topics researchers have looked into the past, but also into the new challenges they will face in the future. Thus, the purpose of this study is to provide a thorough a bibliometric overview of the theoretical framework and to identify beneﬁts and barriers of marketing in the public sector. We provide an overview of the theoretical framework and identify the beneﬁts and barriers of marketing in the public sector through a bibliometric study. To achieve this objective, a systematic literature review was conducted of 3926 articles from 1931 to 2020. The results allowed the identiﬁcation of four main theoretical clusters: educational, public health, social economics and urban politics. It also o ﬀ ered beneﬁts and barriers in the context of MPS. Conclusions and implications to the academia and managers are drawn. Future research opportunities are also provided.


Introduction
Today, as in the past, market competition among organizations (public or private) continues to increase and intensify. This hard reality reminds organizations that they can no longer aim solely for the profit without considering the sustainability of local resources and social wellbeing. A new perspective was identified in the literature (Kotler and Levy 1969;Kotler and Zaltman 1971) in the late 70s, which considered the society more than a place to sell products and services. This perspective, resulting from a transaction and financial focus, moved into a more complex arena. In this arena, marketing concepts beyond the traditional marketing and commercial domain (Balabanis et al. 1997) were used by the public sector to answer society's needs and wants.
The MPS (marketing of public sector) is much more than adapting or using traditional marketing strategies, in the same way that its influence is more than creating a positive image Soc. Sci. 2020, 9, x FOR PEER REVIEW 3 of 23 Figure 1. From traditional marketing to nonprofit marketing. Source: Adapted from Kotler and Levy (1969) and Kotler and Zaltman (1971).
However, Bercea et al. (2016, p. 17) posit that a clear distinction exists between profit-oriented organizations (that sell products and services) and the public sector (which has the public interest as the main goal). In this regard, Madill (1998) suggests the presence of several types of MPS: (a) marketing of products and services, in a similar process to any profit-seeking private organization, with the difference lying in the offer of products and services for free or at a lower cost; (b) social marketing, which seeks to promote the "social good" by appealing to the public's behaviors and attitudes adjustments (e.g., usage of public transports); (c) policy marketing, also trying to change consumers' perceptions and attitudes, about specific policies or new legislation; (d) demarketing, recommending and persuading the public in general, but also specific groups not to use products, services, that are not available anymore or that are not recommended. Proctor (2007), on the other hand, takes a similar position and looks at MPS also as a place of marketisation in which the public "arena" like the traditional market, is defined by the competitiveness of products and services, quality and costs. The author also claims MPS is used to promote organizations' and cities interest to attain higher awareness among the public, authorities and market. Lastly, Proctor (2007) affirms that in the MPS political marketing is used for the promotion of political values, beliefs and goals.
Furthermore, regarding customers, these can vary between politics which are responsible for managing the public sector (Gorton 2016) and citizens (Andersson and Getz 2009) (as private individuals or collective organizations). In sum, the MPS covers extensive and complex phenomena, from the social to the political or legal. As Kaplan and Haenlein (2009, p. 198) suggest "…there is a place for public marketing, i.e., the application of marketing concepts and tools for public administration". Nevertheless, managers and researchers have to take into consideration that there are limits (example, the traditional 4 P's) within the traditional marketing (Bercea et al. 2016). Neglecting those limits or not seeking a better understanding of the MPS framework and its benefits and barriers, would only intensify the degree of uncertainty and increase the restrictions.  Kotler and Levy (1969) and Kotler and Zaltman (1971).
However, Bercea et al. (2016, p. 17) posit that a clear distinction exists between profit-oriented organizations (that sell products and services) and the public sector (which has the public interest as the main goal). In this regard, Madill (1998) suggests the presence of several types of MPS: (a) marketing of products and services, in a similar process to any profit-seeking private organization, with the difference lying in the offer of products and services for free or at a lower cost; (b) social marketing, which seeks to promote the "social good" by appealing to the public's behaviors and attitudes adjustments (e.g., usage of public transports); (c) policy marketing, also trying to change consumers' perceptions and attitudes, about specific policies or new legislation; (d) demarketing, recommending and persuading the public in general, but also specific groups not to use products, services, that are not available anymore or that are not recommended. Proctor (2007), on the other hand, takes a similar position and looks at MPS also as a place of marketisation in which the public "arena" like the traditional market, is defined by the competitiveness of products and services, quality and costs. The author also claims MPS is used to promote organizations' and cities interest to attain higher awareness among the public, authorities and market. Lastly, Proctor (2007) affirms that in the MPS political marketing is used for the promotion of political values, beliefs and goals.
Furthermore, regarding customers, these can vary between politics which are responsible for managing the public sector (Gorton 2016) and citizens (Andersson and Getz 2009) (as private individuals or collective organizations). In sum, the MPS covers extensive and complex phenomena, from the social to the political or legal. As Kaplan and Haenlein (2009, p. 198) suggest " . . . there is a place for public marketing, i.e., the application of marketing concepts and tools for public administration". Nevertheless, managers and researchers have to take into consideration that there are limits (example, the traditional 4 P's) within the traditional marketing (Bercea et al. 2016). Neglecting those limits or not seeking a better understanding of the MPS framework and its benefits and barriers, would only intensify the degree of uncertainty and increase the restrictions.

Method and Bibliometric Variables
A systematic literature review consists of a process to "summarize in an explicit way, what is known and not known about a specific practice-related question" (Briner et al. 2009, p. 19). To assist the systematic literature review, a bibliometric analysis, common type of analysis employed in several disciplines, particularly in the marketing field was performed (Palmatier et al. 2006;Szymanski and Henard 2001). The aim of the study is to provide an overview of the theoretical framework and identify the benefits and barriers of marketing in the public sector. For this purpose, the bibliometric stages and processes undertaken in the analysis were based on an adaptation of Duque-Acevedo et al.'s (2020) procedures. The decision to select this study method was because of the method's efficiency, reproducibility and scientific reliability.

Data Source and Sample Analyzed
The source selected for the search and analysis of the articles was Scopus repository (www.scopus. com). This database is frequently used by researchers to perform bibliometric reviews (Ha et al. 2020;Ribeiro et al. 2020;Saura 2020) due to the size and quality of its database. In effect, the 3926 articles retrieved in the final sample provide a clue of the dimension and importance of the repository.

Main Stages of the Process
Following the procedures identified in Duque-Acevedo et al.'s (2020) study, the bibliometric review considered three stages. The first stage consisted of the definition of the search criteria. The search was conducted on 7 September 2020, in the Scopus database, using the following keywords (see Table 1). The search strings allowed to identify a potential sample between 905 to 28,809 articles.  In the second stage, the manuscripts were subject to a selection of bibliographic databases and documents for analysis. This meant that the previously identified articles (i.e., in the search criteria stage) were the object of a screening process to confirm the articles fitted the study's goals. An initial screening of the title, abstract and keywords to 10% of the sample was made (Pickering and Byrne 2014). Our findings demonstrated the need to refine the search, due to the extensive number of subjects and the wide scope of the studies being incorporated in the data collected (e.g., Medicine, Arts and Humanities, Engineering) (deMatos et al. 2020). Thus, the authors agreed to limit the subject of the search to social sciences.
Moreover, following similar decisions in other studies (Geissdoerfer et al. 2017), only peer-reviewed articles in English were deemed acceptable, to ensure that all documents had gone through a double-blind review screening process and were capable of being useful in the content analysis stage (by using only one language, English). No other limitation was applied to the parameters available in the Scopus repository, either regarding the source title, authors' name, country, affiliation, etc.
The third stage involved data process, systematization and data analysis. The full list of the 3926 articles, composed of title, abstract and keywords was exported and download into a RIS file. Next, this file was open in a reference manager (Mendeley) for another round of screening (title, abstract, keywords) by two of the authors to assess 10% of the sample for its relevance and decision on inclusion/exclusion in the study (Pickering and Byrne 2014). This time, the findings showed that the articles fitted the study's scope and methodological criteria. The RIS file with all the articles was afterwards exported to software supporting the scientific mapping, VOSviewer (deMatos et al. 2020;Duque-Acevedo et al. 2020). According to van Eck and Waltman (2019, p. 3) "VOSviewer is a software tool for creating maps based on network data and for visualizing and exploring these maps". The study followed van Eck and Waltman's (2014) suggestion of a minimum of 10 occurrences due to the large number of these occurrences only 60% of the terms were selected to prevent overflow of data to analyze. Fractional counting was also selected, since it considers equal weight in every action, in opposition to full counting (Perianes-Rodriguez et al. 2016). The software generated bibliometric maps, which helped to identify the most important and frequent occurrences or topics in the retrieved database (van Eck and Waltman 2019). The occurrences and co-occurrences words identified in the bibliometric maps were then used as keywords to search in the reference manager (Mendeley), studies which had addressed those occurrences or topics, visualized in the bibliometric maps. The full texts were assessed by content analysis to interpret data and themes from the articles (Geissdoerfer et al. 2017) to name the clusters and identify the main benefits and barriers to marketing in the public sector.

Period and Variables Analyzed
The first study retrieved was published in 1931, addressing the welfare of the meat industry by the American Meat Packers and the latest in 2020, covering various topics (e.g., urban congesting charging using public infrastructures) (Sugiarto et al. 2020). In the end, a review covering a period of 89 years was undertaken. The high number of peer-reviewed articles selected and their theoretical and empirical content led to exploring the following findings:

Graphic Representation of the Data
The data were imported into the software VOSviewer, which performs visualization of similarities (VOS) and multidimensional scaling, to generate bibliometric maps (deMatos et al. 2020; van Eck and Waltman 2019). After running the software, 5 clusters were generated and 608 items or topics were found. The screening, followed by the analysis of the clusters' outputs, led the authors to exclude one cluster (cluster number 5), considered an outlier, because of the low quality of the items generated by the software and their reduced number, i.e., only 23 items were generated into one clustered (3.7% of a sample) and most of these items were verbs (e.g., turn) or nouns (e.g., link).

Results and Discussion
The bibliometric study findings of the 3926 articles retrieved were divided into two different analysis. First, a more descriptive analysis was made to find the main contributors to the MPS topics. Second, an analysis was made and examination of the clusters was generated using VOSviewer.

Main Contributors
The 3926 articles were published mostly over the past three decades (Figure 2). In effect, researcher interest reached its peak in the Scopus database in the last two years (2018-2019). The findings of the study suggest MPS was since early years an important topic, which to some extent was neglected until the 1990s.

Results and Discussion
The bibliometric study findings of the 3926 articles retrieved were divided into two different analysis. First, a more descriptive analysis was made to find the main contributors to the MPS topics. Second, an analysis was made and examination of the clusters was generated using VOSviewer.

Main Contributors
The 3926 articles were published mostly over the past three decades (Figure 2). In effect, researcher interest reached its peak in the Scopus database in the last two years (2018-2019). The findings of the study suggest MPS was since early years an important topic, which to some extent was neglected until the 1990s.  Year 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005  The journals which had most articles published about MPS topics ( Figure 3), were tobacco control (3%), social science and medicine (2%), public relations review (2%), sustainability Switzerland (1.9%) and telecommunications policy (1.7%).

Results and Discussion
The bibliometric study findings of the 3926 articles retrieved were divided into two different analysis. First, a more descriptive analysis was made to find the main contributors to the MPS topics. Second, an analysis was made and examination of the clusters was generated using VOSviewer.

Main Contributors
The 3926 articles were published mostly over the past three decades (Figure 2). In effect, researcher interest reached its peak in the Scopus database in the last two years (2018-2019). The findings of the study suggest MPS was since early years an important topic, which to some extent was neglected until the 1990s.  Year 1935 1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005  The authors that published most articles were P.M. Ling (11 articles), followed by three authors with 7 articles each, F. J. Chaloupka, S. A. Glantz, K. M. Ribisl (Figure 4). One researcher, P. M. Ling, in particular, was crucial to establish the biggest network found. Soc. Sci. 2020, 9, x FOR PEER REVIEW 7 of 23 The authors that published most articles were P.M. Ling (11 articles), followed by three authors with 7 articles each, F. J. Chaloupka, S. A. Glantz, K. M. Ribisl (Figure 4). One researcher, P. M. Ling, in particular, was crucial to establish the biggest network found.  If these five groups highlight the importance of creating networks, the findings also reveal, that most authors do not have extensive networks. This indicates to a certain extent the need to increase networks among MPS scholars. Soc. Sci. 2020, 9, x FOR PEER REVIEW 7 of 23 The authors that published most articles were P.M. Ling (11 articles), followed by three authors with 7 articles each, F. J. Chaloupka, S. A. Glantz, K. M. Ribisl (Figure 4). One researcher, P. M. Ling, in particular, was crucial to establish the biggest network found.   The nationality of the authors is by majority from a native-English-speaking country. As Figure  7 shows, the top three countries are USA (38%), United Kingdom (13%), Australia (7%). Despite some diversity having been found among the authors' nationality, this study's findings highlight the need for more investment by researchers from other nationalities, since each country has each own culture and socioeconomic policies. The nationality of the authors is by majority from a native-English-speaking country. As Figure 7 shows, the top three countries are USA (38%), United Kingdom (13%), Australia (7%). Despite some diversity having been found among the authors' nationality, this study's findings highlight the need for more investment by researchers from other nationalities, since each country has each own culture and socioeconomic policies. Soc. Sci. 2020, 9, x FOR PEER REVIEW 8 of 23 The authors with most published articles were affiliated ( Figure 6) with The University of California (34 articles), Michigan State University (28 articles), The University of British Columbia (26 articles), The University of North Carolina at Chapel Hill (26 articles) and The University of Sydney (25 articles). These top five universities showed the predominance of American Universities and the western universities in general as the theoretical background of the research on MPS. The nationality of the authors is by majority from a native-English-speaking country. As Figure  7 shows, the top three countries are USA (38%), United Kingdom (13%), Australia (7%). Despite some diversity having been found among the authors' nationality, this study's findings highlight the need for more investment by researchers from other nationalities, since each country has each own culture and socioeconomic policies. Another information sought in the bibliometric study was to identify which institution had invested more in funding MPS research (Figure 8). The National Institutes of Health (28 articles) followed by the National Cancer Institute (24 articles) and the Economic and Social Research Council (20 articles) were the three main contributors. Soc. Sci. 2020, 9, x FOR PEER REVIEW 9 of 23 Another information sought in the bibliometric study was to identify which institution had invested more in funding MPS research (Figure 8). The National Institutes of Health (28 articles) followed by the National Cancer Institute (24 articles) and the Economic and Social Research Council (20 articles) were the three main contributors.

Identifying Main Clusters and Topics in MPS
A total of 3926 articles, covering 89 years (1931-2020) of publications were obtained. The bibliometric sample data retrieved from Scopus was assessed by VOSviewer overlay visualization, leading to analyze the networks established over time among the different (period of 1980-2020), as shown in Figure 9, composed of a color bar (lower right corner of the visualization), indicating the correspondence between colors and years of publishing. The topic that generated the most occurrences were market, production and price, in the Year 2000. From mid-2000 to 2010, city, student campaign, message, regulation and advertising are the most repeated in the database. After 2010 to 2020, social medium, blog, content, Facebook and Twitter are among the newest topics.

Identifying Main Clusters and Topics in MPS
A total of 3926 articles, covering 89 years (1931-2020) of publications were obtained. The bibliometric sample data retrieved from Scopus was assessed by VOSviewer overlay visualization, leading to analyze the networks established over time among the different (period of 1980-2020), as shown in Figure 9, composed of a color bar (lower right corner of the visualization), indicating the correspondence between colors and years of publishing. The topic that generated the most occurrences were market, production and price, in the Year 2000. From mid-2000 to 2010, city, student campaign, message, regulation and advertising are the most repeated in the database. After 2010 to 2020, social medium, blog, content, Facebook and Twitter are among the newest topics. Soc. Sci. 2020, 9, x FOR PEER REVIEW 9 of 23 Another information sought in the bibliometric study was to identify which institution had invested more in funding MPS research (Figure 8). The National Institutes of Health (28 articles) followed by the National Cancer Institute (24 articles) and the Economic and Social Research Council (20 articles) were the three main contributors.

Identifying Main Clusters and Topics in MPS
A total of 3926 articles, covering 89 years (1931-2020) of publications were obtained. The bibliometric sample data retrieved from Scopus was assessed by VOSviewer overlay visualization, leading to analyze the networks established over time among the different (period of 1980-2020), as shown in Figure 9, composed of a color bar (lower right corner of the visualization), indicating the correspondence between colors and years of publishing. The topic that generated the most occurrences were market, production and price, in the Year 2000. From mid-2000 to 2010, city, student campaign, message, regulation and advertising are the most repeated in the database. After 2010 to 2020, social medium, blog, content, Facebook and Twitter are among the newest topics. The same data sample in the label view (Figure 10), showed the topics and helped us delimit them into clusters. Their rank is represented by the size (more occurrences) of the node presented. The clusters are represented by different colors and their connection is established by the proximity to each other. For example, the closer the clusters are to each other, the stronger the networks between the clusters and topics. The findings revealed four main clusters: Cluster 1-educational, Cluster 2-public health, Cluster 3-social economy and cluster 4-urban politics. Soc. Sci. 2020, 9, x FOR PEER REVIEW 10 of 23 The same data sample in the label view (Figure 10), showed the topics and helped us delimit them into clusters. Their rank is represented by the size (more occurrences) of the node presented. The clusters are represented by different colors and their connection is established by the proximity to each other. For example, the closer the clusters are to each other, the stronger the networks between the clusters and topics. The findings revealed four main clusters: Cluster 1-educational, Cluster 2public health, Cluster 3-social economy and cluster 4-urban politics. The areas identified and outlined in Figure 10, reveal that Cluster 2 (public health) is the one with the greatest dimension, emphasizing the importance researchers gave to this topic. However, to identify benefits and barriers among all the clusters, these are explored individually, including a brief discussion stressing the most relevant topics.

Cluster 1-Educational
The first identified cluster was educational and the topics most addressed were student (805 occurrences), library (562 occurrences), university (440 occurrences) and public relation (428 occurrences). The public schools and universities faced in the past several difficulties (Cardoso et al. 2011;Hanson and Henry 1992 The areas identified and outlined in Figure 10, reveal that Cluster 2 (public health) is the one with the greatest dimension, emphasizing the importance researchers gave to this topic. However, to identify benefits and barriers among all the clusters, these are explored individually, including a brief discussion stressing the most relevant topics.

Cluster 1-Educational
The first identified cluster was educational and the topics most addressed were student (805 occurrences), library (562 occurrences), university (440 occurrences) and public relation (428 occurrences). The public schools and universities faced in the past several difficulties (Cardoso et al. 2011;Hanson and Henry 1992;Ives and Schulz 1995;Katzir and Perry-Hazan 2019;Minhas and Perret 2017;Pashootanizadeh and Rafie 2020;Singh 2016;Taylor et al. 2014;Vukovič et al. 2010). The first was the attempt to keep their economic sustainability and a traditional way of teaching (Miles et al. 2017) free from the bonds of new university enterprises (Cardoso et al. 2011). The second was to maintain their role in providing equal opportunities to every student, independently of the setting (e.g., urban, suburban or rural regions). The third was the social context facilitating the marginalization and exclusion (Olson Beal and Beal 2016;Posey-Maddox et al. 2014) of students, requiring, therefore, a higher degree of involvement and participation of parents, families and communities (Singh 2016). In this regard, a novel study from Potterton (2020, p. 166) introduced the concept of parental accountability, which refers to " . . . the sensemaking, experiences and consequences that are related to decision-making in a school choice environment, wherein parents' feelings about their child's schooling may be intense, emotionally stressful, malleable, cyclical and ongoing-not static". The roles social media was also explored, from the perspective of the offer side and demand. For example, Pashootanizadeh and Rafie (2020) investigated how public librarians' usage of social media was viewed by librarian users. They found that interaction capability is the most valued aspect by library users.

Cluster 2-Public Health
Cluster 2-public health was represented mainly by the following nodes: campaign (663 occurrences), health (408 occurrences), regulation (393 occurrences) and advertising (297 occurrences). Public health policies in the past decades (Burris 2008;Choi and Springston 2014;Evashwick and Ory 2003;Freeman et al. 2016;Garrett et al. 2019aGarrett et al. , 2019bHa and Ferguson 2015;Lozano et al. 2015;Mahmood et al. 2019;Maynard 1986;Norén 2010;Strand 2019) were important for the promotion of behavioral and lifestyle changes, i.e., healthier lifestyle. One such action was the tobacco visual displays in product packages (Alemanno 2011) to reduce consumption among smokers and call for public awareness. Contradictory to this situation, other organizations have marketed their products (e.g., tobacco, food, soft drinks) using storytelling and brand aid to reach and attain consumer engagement. In addition, a crucial change occurred in the social and economic setting which "posit the individual as responsible for the management of their own bodies and selves in late modern societies characterized by 'government at a distance' and the repeal of welfare" (Crawshaw 2014(Crawshaw , p. 1127. In this context, Crawshaw (2013) and Crawshaw (2014) also argued that social scientists fought for equity and social justice. The economic changes (Alemanno 2011;Bernauer and Meins 2003;Harriss-White 1995;Kaplan 2016;Liou 2016) came from socio-economic innovations in the market driven by technology and transportation, obliged authorities to regulate the technology, biotechnology agriculture (e.g., genetically modified organisms), biomedical (e.g., regenerative therapies) and public health problems (Alemanno 2011) related with alcohol addiction, tobacco, obesity or even internet health scams (Garrett et al. 2019b). One the other hand, technology also brought positive changes to the market and good options to consumers. Al Dahdah's (2019) investigation looked at the global market dynamics and its commodification associated with mobile programs (mHealth) used to help patients with their health appointments and health care. Other studies (Dijkhuizen et al. 2013;Freeman et al. 2016;Knai et al. 2015;Penders and Nelis 2011) emphasized food advertising campaigns dealing with starvation and/or lack of resources. Besides, they addressed food fortification as a way to reduce costs, combat children micronutrient deficiency and also as a strategy to attain a sustainable balance between the needs and wants of the world population (Dijkhuizen et al. 2013). A similar balance was required legally between the consumers' digital information and how that information is used by datacenters and operated in the big data environment.

Cluster 3-Social Economy
Social economy was Cluster 3, with the most recurrent topics being: market (1231 occurrences), case (610 occurrences), cost (398 occurrences), production (365 occurrences) and economy (284 occurrences). The social cluster (Arnaud 2016;Chriss 2015;Fox 1988;Gaffney 1997;Garg 2015;Konda et al. 2015;Low and Davenport 2009;Phyne 1996;Szablewska and Kubacki 2019;Zepeda et al. 2003; Zhou and Ye 2019) revealed market developments that led to researchers assessing the fair trade (Low and Davenport 2009) and the importance of production from different origins and methods, e.g., agricultural (Zhang and Owiredu 2007) and biotechnology (Zepeda et al. 2003). Furthermore, Ethics and ethical policies in trade movements were also considered (Scranton 1995), due to the impact it has on consumers' perception and trust. The previous studies also investigated and compared public perceptions and initiatives regarding sustainable policies and green marketing (Garg 2015).
The reason lied mainly in the economy in general and markets in particular working badly, since public agencies and organizations failed in managing the limited natural resources available in the market (Gaffney 1997). One of the changes that occurred was the use of entrepreneurial principles to meet social needs and wants to attain the social wellbeing (Konda et al. 2015) because of the deficient understanding of the specific structural characteristics of the markets and the changes in society in general (Bergsten 1985). Zhou and Ye (2019), for instance, sought to uncover the factors that influence crowdfunding for nonprofit projects. Their findings highlighted how important network and viral marketing are within the Chinese context. Other authors, considered social good and social marketing, a topic addressing societal and individual welfare (Szablewska and Kubacki 2019). In Szablewska and Kubacki's (2019) study several crucial topics were debated. For example: "What is the societal good?", "Who decides what is beneficial for the society?" or "In which context is it beneficial or not?" In the end, the authors highlighted the need for a human rights approach.

Cluster 4-Urban Politics
The fourth cluster, urban politics, incorporated city (611 occurrences) tourism (407 occurrences), image (456 occurrences), society (320 occurrences) and culture (310 occurrences) nodes. Public marketing concepts were applied in developed countries to help cities face economic growth and environmental challenges. On one end, some researchers focused on designing and planning better urban spaces (e.g., transportation system) (Ashworth and Voogd 1990;Mercer and Mayfield 2015). On another end, urban politics addressed urban culture and how to market cities or destinations, but also events (Johansson and Kociatkiewicz 2011) or mega-events (Santos et al. 2017) and activities like tourism (Morris and Fridgen 1994;Rabbiosi 2015;Schloegel 2007;Uysal and Crompton 1985). Thus, selling cities meant urban politician and managers needed to developed city branding (Han et al. 2018;Joo and Seo 2018;Santos et al. 2017) and promote an attractive city image (Avraham 2004), even when dealing with a crisis in communication and promotion that affected visitors' trust (Avraham 2013;Seraphin et al. 2018). In addition, such communication strategies were used in underdeveloped countries or markets in a parastatal situation, in which public entities needed to rely on urban politics and actions) to reduce markets surplus or deficits, e.g., starvation in Africa (Child et al. 1985). This reinforced the power of politics and, consequently, several authors (Balestrini and Gamble 2011;Child et al. 1985;Chowdhury and Naheed 2019;Hadjimanolis 2010;Haenschen and Wolf 2019;Lambert and McGuire 1990;Pykett et al. 2014;Sandercock and Dovey 2002;Simons 2019;Wymer et al. 2013) focused on the changes which occurred in the political public context. Among these changes was the governmental and political practice of marketing principles (Pykett et al. 2014) as a persuasive form of communication to achieve higher and better public engagement, perception and image (Wymer et al. 2013). Chowdhury and Naheed's (2019) studies were among those which investigated how politicians could sway their voters to vote for them. In their studies, rural voters demonstrated to be influenced by celebrities, national leaders and symbols. Political communication and political image (Simons 2019) were important research topics throughout the years, not boosted by the social media and social networks new communication channels (Larsson 2019). These developments on the political and social networks emphasized need to regulate (e.g., political advertising of online and offline campaigns) (Haenschen and Wolf 2019). Overall, this scenario contributed to the use of marketing for " . . . the arena of party political electoral competition, ignoring how it could be developed further into the area of interest groups generally and, more specifically, into an examination of how organizations attempt to influence public policy" (Harris and McGrath 2012, p. 75).

Benefits and Barriers in MPS
In the density visualization of Figure 11, the topics can be seen by their label (size) and color. As mentioned by van Eck and Waltman (2014), this view provides a general overview of the map and signals the most important areas. In addition, the "Terms [topics] occurring in the same document are placed close to each other and frequently mentioned terms are displayed in a larger font size than more infrequently occurring terms." (Broström and Karlsson 2017, p. 12). In other words, it is in the red areas or topics with bigger size that the larger number of topics and weights of the neighboring can be found. Conversely, the blue area is the one with a smaller number of topics, neighborhood and weight. Figure 11 shows the topics market, student, campaign, regulation and library as the main areas. Thus, from Figure 11, the topics with less size are the ones with a smaller number of topics, neighborhood and weight. In these areas, several benefits and limitations can be found in each cluster. Soc. Sci. 2020, 9, x FOR PEER REVIEW 13 of 23 more infrequently occurring terms." (Broström and Karlsson 2017, p. 12). In other words, it is in the red areas or topics with bigger size that the larger number of topics and weights of the neighboring can be found. Conversely, the blue area is the one with a smaller number of topics, neighborhood and weight. Figure 11 shows the topics market, student, campaign, regulation and library as the main areas. Thus, from Figure 11, the topics with less size are the ones with a smaller number of topics, neighborhood and weight. In these areas, several benefits and limitations can be found in each cluster. Figure 11. Density map . Source: authors using VOSviewer software.
Among the benefits this review found were, maternal education (educational cluster), better breast cancer prevention (public health cluster), the reduction of domestic violence (social economy cluster) and improved urban economy (urban politics cluster). On the other hand, there are still barriers to overcome in all four clusters, mainly those addressing how to manage the relationships between social media platforms and universities for better public services (educational cluster), how to increase organ donations (public health), lack of market innovation (social economy cluster) and urban development and destination promotion (urban politics cluster).  . Source: authors using VOSviewer software.
Among the benefits this review found were, maternal education (educational cluster), better breast cancer prevention (public health cluster), the reduction of domestic violence (social economy cluster) and improved urban economy (urban politics cluster). On the other hand, there are still barriers to overcome in all four clusters, mainly those addressing how to manage the relationships between social media platforms and universities for better public services (educational cluster), how to increase organ donations (public health), lack of market innovation (social economy cluster) and urban development and destination promotion (urban politics cluster).
Although MPS is still in its early infancy when compared with other constructs, its magnitude is evident when taking into consideration the number of topic and areas it covers. As illustrated in Figure 12, using a world cloud software for a visual representation, the most frequent word (the one with greater size) is public, followed by marketing and health, among the 3926 articles' titles. In this regard, Other words, such as social, market, food, policy, tobacco, service, development and analysis, demonstrate the extension of the scope of MPS (e.g., from social to politics) and the specifics of this sector (tobacco, food, services), but also at the same time, benefits and barriers that must be addressed and overcome. Although MPS is still in its early infancy when compared with other constructs, its magnitude is evident when taking into consideration the number of topic and areas it covers. As illustrated in Figure 12, using a world cloud software for a visual representation, the most frequent word (the one with greater size) is public, followed by marketing and health, among the 3926 articles' titles. In this regard, Other words, such as social, market, food, policy, tobacco, service, development and analysis, demonstrate the extension of the scope of MPS (e.g., from social to politics) and the specifics of this sector (tobacco, food, services), but also at the same time, benefits and barriers that must be addressed and overcome.

Conclusions
The study's main goal was to provide an overview of the theoretical framework and to identify the benefits and barriers of marketing in the public sector (MPS). After nearly nine decades it can be said MPS is reaching maturity in certain topics (market, student, campaign and health). A total of four clusters were identified, namely, Cluster 1-educational, Cluster 2-public health, Cluster 3-social economy and cluster 4-urban politics. The extensive number of articles found testify for the diverse and sound theoretical framework.
Regarding the first goal, the main contributors to the current framework, this study found that mostly was published after 1990s, despite the initial work found reporting back to 1931.
Findings revealed an absence of intense research during many years , showing a lack of investment by the academia on the MPS. This study found that the journals with most articles published were very diverse and covered different aspects of the MPS concept, i.e., tobacco control, social science and medicine, public relations review, sustainability Switzerland and telecommunications policy. The authors (e.g., Pamela M. Ling) and institutions were mostly from the USA and western countries. The USA is particularly a country with great impact and contribution to the research made to date, representing almost 40% of the sample's articles. Moreover, this contribution was also found on the funding institutions with The National Institutes of Health (USA) being the one that funded the most articles.
Regarding the second goal, the main benefits MPS brought were: (a) support of maternal education, promotion of equality of opportunities and demand for health education (educational cluster); (b) better prevention against breast cancer, improved understanding of genetically modified food consequences, promotion of physical activity and awareness for the hazards of pesticides (public health cluster); (c) greater social integration and a better understanding of domestic violence circumstances (social economy cluster) and (d) strengthening of the urban economy, political legitimacy and support for the political engagement (urban politics cluster).
However, this study found that barriers still exist with managers (Laing and McKee 2001) and scholars (Butler and Collins 1995;Connolly 1991) working in the public sector still pondering the question of whether marketing should be used in public administration. Despite these doubts, results show the main barriers to be overcome are those regarding; (a) relationship between schools, communities and organizations, within different cultural backgrounds at a time the social media platforms increasingly influence the public services (educational cluster); (b) organ donation, financial costs, alcohol public acceptance are crucial topics, along with the legal requirements to access the markets or lack of e-regulation (public health cluster); (c) Lack of market innovation, low level of social responsibility, growth of economic exclusion, social change avoidance, political power pressure, persistent political instability (social economy cluster); and (d) Restrictions to city development, lack of trust on city brand and image and slow adoption of innovative behaviors (urban politics cluster).
Moreover, the theoretical implications of this study's bibliometric analysis enabled researchers to have a new methodology to comprehend and enhance the knowledge on the MPS construct. As Perianes-Rodriguez et al. (2016) noted, the bibliometric studies allow for the structure and evolution of constructs to be distinguished and its details found. Managerial implications reinforce previous assumptions, recognized by Kotler and Zaltman (1971) and Kotler and Levy (1969), that marketing techniques and tools, commonly applied to products and services, are also susceptible to be applied to public, nonprofit and social marketing in the public sector in a broader sense. Moreover, the most relevant question should not be, "How can marketing be used in the public sector?" Instead, the question should focus on how we can transfer the advancements and contribution of the theoretical framework to market practitioners and managers, since previous research, made the past, shaped the present and will impact on the future. If managers are more and better informed, the success and competitiveness of their organizations will increase.

Limitations and Future Avenues for Research
The present research focuses on a conceptual nature, lacking an investigation into the similarities and differences among MPS, the different school of thought (e.g., Nordic school versus American school). In addition, the study ranged from 1931 to 2020, using solely Scopus database, reducing the literature produced in other technologic tools. Future analysis of bibliometric data should consider other keywords, other databases and different methodologies for analysis (for instance, inductive content analysis). Moreover, the mapping software used allowed to identify the authorship, co-authorship, affiliation and nationalities, but a more in-depth analysis may help to have a more detailed picture of the other contributors, construct(s) (citations, seminal papers) and evolution of several theoretical and methodological frameworks. The current pandemic context due to COVID-19, encloses potential avenues for research in the future regarding the urban, social, educational, economic and health changes MPS will face within the national and international boundaries.