Dealing with complexity – the state of problem structuring methods in Europe and beyond

In an era that is characterised by fast technological progress and accelerated change, the world around us is not short of complexity and increased volatility. Ongoing or new challenges, such as poverty, human trafficking, conflict and lack of democracy in so many parts of the word, create further uncertainty and affect millions of people around the globe. In such complex environments, managers and leaders of organisations and societies often struggle to find ways to meet expectations and to move forward.

The challenges that organisations and societies face are unpredictable and often interrelated in several ways. For example, the Covid-19 virus which started as a health problem soon became a deadly pandemic with serious economic, psychological, social and other implications. Also, the current ongoing conflicts in Europe and the Middle East, apart from the high level of human suffering they created, have also contributed to a serious energy crisis and caused much financial hardship and high levels of anxiety to people in many different countries. In the management science literature such problems are often described as “messy” or “wicked”. Their key characteristic is that they tend to cross agency, stakeholder, jurisdictional and other boundaries, and typically confound bureaucratic government departments and decision-makers (Sydelko et al., 2023).

Within the broader analytical field of operational research (OR), problem structuring methods (PSMs) provide a group of approaches which are highly analytical but non-mathematical and at the same time place heavy emphasis on the inclusion and participation of all relevant stakeholders in the entire modelling process. As such, PSMs allow for a wide range of different stakeholder views of a problematic situation to be expressed, explored and accommodated, and can therefore provide important decision support in situations characterised by high levels of complexity and possibly conflict among the stakeholders. Like the wider OR discipline itself, PSMs have their own history of successful development and application, and have made an important contribution to the field of management science (Kogetsidis, 2024a).

This paper aims to identify the level of use of facilitated modelling with PSMs within the analytical discipline of OR by carrying out a review of applications of PSMs that have been published in discipline-based journals over the last 15 years. The paper starts with a brief overview of the nature of both OR and PSMs, which offers an account of the main characteristics that the two fields have, as well as the theoretical assumptions that each field makes about the nature of the world and knowledge. It then offers the results of a recent review of PSMs, which aims to identify the current state of this important domain of analytical work and its application in different parts of the world. The review also aims to identify the level of use of PSMs across different applications and problem domains. The paper concludes with some directions for future research.

This paper contributes to the relevant literature of management science in two ways – firstly, by raising awareness among managers and leaders of organisations in relation to the unique contribution that this important domain of analytical work can make in problem situations that are characterised by increased complexity; and secondly, by providing an up-to-date account of the state of the field in different countries and across different problem domains. In that respect, the findings are expected to be of value to both operational researchers, who are constantly engaged with improving existing and/or coming up with new analytical methods and tools, and managers and leaders who are looking for ways of managing the increased levels of complexity, turbulence and volatility and their impact on organisations and societies.

OR emerged in the UK in the late 1930s and during the crucial period of preparations ahead of the Second World War. The aim was to provide a new analytical approach, with a holistic and multi-disciplinary orientation, in order to provide assistance in improving the strategic and tactical effectiveness of military systems in battle. After the end of the war, OR moved to industry and government and developed its analytical methods and tools further. This was particularly evident in the 1950s, the so-called “golden-era” of the new discipline, when OR entered academia and was established as a formal discipline with the creation of the first OR professional societies around the world.

OR, from its early start, had a very analytical and scientific approach to problem-solving, something that became more evident during the “golden-era” of the discipline, when many of its methods and tools were developed. This, however, led to the new discipline eventually to focus almost exclusively on problems or applications with clear goals, where the objective was often the optimisation of some quantity in the face of known constraints. The implication of this was that, even though the new discipline had become very successful in areas such as transportation, project scheduling and forecasting, where the goals tend to be clear, it faced difficulties in addressing more complex problems involving unclear or non-agreed objectives, as well as differences in the views, interests and expectations of the stakeholders. As complex problems tend to have many different dimensions, the traditional scientific approach of breaking them down into discrete parts and implementing standardised solutions does not seem to be effective in complex, social environments, where increased complexity, disagreement and often conflict tend to be the norm. This realisation brought the discipline into a period of crisis, which reached its peak in the 1970s. The criticisms expressed by some of the pioneers of OR in terms of the direction that the discipline had taken, and particularly its move away from its multi-disciplinary and holistic orientation, paved the way for a new body of work which, a few years later, would become largely known as PSMs or “soft OR”.

PSMs are based on the key assumption that different stakeholders may have very different perceptions regarding the problem situation – i.e. they could each have a very different view of what the problem is or what needs to be done to improve the situation. On top of that, different stakeholders tend to have their own goals, interests and priorities, which would typically result in disagreement and sometimes conflict among the stakeholders. PSMs allow for a range of different views of the problematic situation to be identified, explored and accommodated so that commitment to action can be reached. To enable all types of stakeholders to understand and actively participate in the modelling process, PSMs use diagrammatic modelling and therefore favour a qualitative, rather than quantitative, approach to problem-solving. OR practitioners are still involved in the modelling process but now take on the role of facilitator, whose prime task is to enhance the conversation between the participants and to help them identify critical issues within the system (Tavella and Papadopoulos, 2017). This is very different from classical OR, where the OR practitioner would be expected to act as the technical expert who would carry out the entire modelling process and make recommendations for action and improvement ^[1].

The theoretical positions of classical OR and PSMs are reflected by the particular ontological and epistemological assumptions they each make about the nature of the world and knowledge. Traditional OR makes the ontological assumption that there is an objective reality and sees systems as entities that exist in the real world. It also follows a positivistic epistemology treating knowledge as hard and real, which can be transmitted in a tangible form. On the other hand, for PSMs, social reality is subjective and dependent on how one perceives a particular situation, based on his or her own experiences, interests and values. The epistemological assumptions these methods make are anti-positivistic, treating knowledge as subjective and based on experience and insight. These ontological and epistemological assumptions that the two strands make also affect the way that they view the relationship between human beings and their environment. In that respect, the hard methods of classical OR assume that human beings respond in a mechanistic or even deterministic way to their environment, while PSMs see individuals as being able to initiate their own actions and therefore to create their environment. More detailed accounts of the theoretical and philosophical positions of classical OR and PSMs can be found in Mingers (2003) and Kogetsidis (2023).

On the other hand, despite their increasing popularity and tremendous contribution to management science, PSMs have been criticised for not being able to handle issues of power dynamics and the asymmetrical distribution of power that often exists among the stakeholders. This has taken methodological developments in a more critical direction, which goes back to the Frankfurt School of social theorists. Furthermore, Ulrich's (1983) work on critical systems heuristics has provided valuable practical guidelines for action on behalf of disadvantaged groups within problem contexts where the unequal distribution of power and resources affects the way decisions are made. The above criticisms in terms of the inability of soft OR to deal with issues of power dynamics, together with the recognition of the importance of methodological pluralism in organisational enquiry, have made the potential for the successful application of PSMs much greater. Today there is widespread evidence of multi-method and multi-paradigm ^[2] interventions (e.g. Abuabara and Paucar-Caceres, 2021; Kogetsidis, 2025a) and approaches such as boundary critique (Midgley, 2000) can assist in the exploration of system boundaries and systemically enhance the application of PSMs (Foote et al., 2007). The plethora of PSMs that exist today, together with the development of new methodological tools from those who take a more critical stance to systemic intervention, have enabled methodological pluralism to dominate in all forms of organisational enquiry.

More recently, a growing interest in the behavioural aspects of OR modelling has produced a new body of work, known as “behavioural operational research (BOR)” (Franco and Hämäläinen, 2016; White et al., 2020; Burger, 2021), which shifts the focus on the participants' behaviour during OR interventions. This exciting new domain of scholarly work examines the development of models that capture human behaviour and therefore seeks to bring the attention of decision makers and researchers on managing the behavioural aspects of the system more realistically (Kunc and Katsikopoulos, 2022). This is of prime importance when it comes to the application of PSMs, as this domain of analytical work is focused on the actual stakeholders affected by a particular problematic situation who now have the opportunity to come together and try to find solutions that would be feasible and acceptable to all. As these participants would now be at the centre of the entire enquiry, their individual personal traits and behaviour as part of the modelling team would be a crucial factor for the success of the project.

Other more recent developments that are relevant to PSMs relate to the theory and practice of systemic innovation. Systemic innovation aims to avoid efforts developed within relatively narrow boundaries, where isolated financial, social, environmental or other single-issue gains can be made, and favours the use of systems approaches as a way of achieving synergistic value creation among stakeholders (Lindhult et al., 2022). This is very much in line with methodologies that have a strong systems orientation and take a holistic view of the problem situation (Kogetsidis, 2013, 2025c), paying particular attention to the many complex interactions between the various parts of any system and to the new emergent properties that this whole exhibits.

Our review of the application of PSMs was based on academic papers published in the main journals of the discipline. These included the Journal of the OR Society (JORS), which is the oldest OR journal in the world published by the British OR Society, and the European Journal of OR (EJOR), the world's largest OR journal published by the Association of European OR Societies (EURO). From the United States, we selected the three OR journals published by the Institute for Operations Research and the Management Sciences (INFORMS), i.e. Operations Research, Management Science and Interfaces, as well as Omega – the International Journal of Management Science, published by Elsevier. These journals were selected on the basis of being the most significant ones in the discipline of OR, which together provide a full and accurate account of the research that is published in relation to this field of scholarly work. As a result, relevant surveys of OR practice (e.g. Paucar-Caceres and Pagano, 2009; Paucar-Caceres and Espinosa, 2011) are often based on these OR journals, rather than adopting a more systematic approach in their search for papers.

Our search covered electronic publications in the above OR journals over the period 2010–2024. The search used the official website of the OR Society (www.theorsociety.com) for papers published in JORS, ScienceDirect (www.sciencedirect.com) for papers published in EJOR and Omega, and the INFORMS database (www.pubsonline.informs.org) for papers published in Operations Research, Management Science and Interfaces. The procedure followed was to search the above databases for the occurrence of specific terms included in the article's title, abstract or list of keywords. The search terms used were “problem structuring methods” and “soft OR”, as well as the names of the three most well-known PSMs of “Soft Systems Methodology (SSM)”, “Strategic Options Development and Analysis (SODA)”/“cognitive mapping”, and “Strategic Choice Approach (SCA)”. The search was made in October 2024.

A filtering process that involved reading the paper's abstract was then used in order to ensure that all the papers identified were relevant to the study. When this was not clear from the abstract, the entire paper was examined. The search produced a total of 130 papers that were relevant to our study. These included all types of research articles, including review papers, but excluded other contributions such as book reviews and short communications. Interestingly enough, all the papers that our search identified came from the two European OR journals, namely the Journal of the OR Society (56 papers) and the European Journal of OR (74 papers), with no relevant papers having been produced by any of the four leading American OR journals. This finding did not come as a surprise and it fully supports the view that operational researchers on the other side of the Atlantic do not actively engage with soft OR and PSMs, as previous studies have shown (e.g. Paucar-Caceres, 2010, 2011).

The papers were then carefully examined and all the practical applications of PSMs they were reporting on were identified. The process followed was to check each paper carefully to examine whether this involved the application of one or more PSM as part of a practical intervention. This process identified the papers that reported on practical case studies on problem structuring interventions, rather than having a different focus or providing a more theoretical coverage of the field. The case studies reported in the papers were then read carefully so that the country or countries that each application took place could be recorded. At the same time, each application was manually classified on the basis of the problem domain it covered. There was no pre-determined list of categories and the problem domains were created at the time of the examination on the basis of the actual focus of these interventions. The process produced several categories, which varied from sustainability and climate change to problems related to health, education and local government. Some categories were subsequently joined together to produce a total of ten different problem domains (for example, applications on sustainability, ecology and environmental management were grouped together to form the domain of “sustainability”, and applications on poverty, marginalisation of communities and drug trafficking produced the category of “societal problems”). When a paper reported on an application that could fit in more than one problem domain, the application was categorised according to the prime focus of the investigation.

An initial analysis of the papers on PSMs published in the two key OR European journals between 2010 and 2024 has shown a steady level of coverage of the field of PSMs over this period. The distribution of papers can be seen on Figure 1, with the peak on the number of papers in the three-year period of 2016–2018 being the result of the publication of two relevant special issues on PSMs in the European Journal of OR in 2018.

The papers found were typically of a very practical nature and reported on actual applications of PSMs. These were either applications of established PSMs, such as SSM or SODA, or the implementation of new approaches in order to deal with problematic situations. A total of 112 applications of PSMs in particular problem contexts were identified, with a small number of papers reporting on multiple applications.

Figure 2 shows the geographical representation of the 112 applications of PSMs. The results show that the great majority of applications (45 cases) have taken place in the United Kingdom, which means that 40% of all the applications of PSMs that have been reported in the two journals over this period have taken place in one particular country. This is followed by Portugal (9 applications), Brazil and USA (6 applications each). Four applications of PSMs were carried out in Italy, Australia and New Zealand, three applications were found in Denmark, Netherlands, Cyprus and China, and two applications took place in Malta, Finland and Colombia. There were also single applications of PSMs in 15 other countries, which covered a wide geographical range from Canada, to Saudi Arabia, Nigeria, Bangladesh and India. Taken together, the actual applications of PSMs reported in the two OR journals over the last fifteen years have covered all continents and a total of 30 different countries around the globe.

The applications of PSMs identified in our study have been classified into a number of different categories on the basis of the main focus that each OR intervention had. These cover ten different application domains, which include both the business sector (applications on behalf of or in relation to commercial organisations) and the wider sector of non-profit organisations (covering a very diverse list of sectors such as defence, health and charity organisations). Table 1 shows the number of applications of PSMs for each sector and geographical region.

A chi-squared test performed on the results found that a statistically significant association existed between geographical region and the domain of application of PSMs. A Monte Carlo simulation and the Fisher-Freeman-Halton test that were also conducted provided further evidence that the distribution of sectors varied systematically across geographical regions, rather than occurring by chance. It can therefore be concluded that in the above results the domain of application of PSMs depends on geographical region in a statistically meaningful way.

Applications of PSMs within commercial organisations tend to focus on issues such as the implementation of new information systems or the need to achieve higher levels of customer satisfaction. Some recent examples include the use of PSMs to help a technology company to become more customer-centric (Hermanto et al., 2022) and the effective management of projects dedicated to the implementation of enterprise information systems in manufacturing firms (Panagiotidis et al., 2023).

As it can be seen from the distribution of applications in Table 1, even though the single highest category of applications (27 cases or 24% of all applications) was in the business sector, the great majority of all PSM applications involved the wider non-profit sector, which included government, local government and not-for-profit organisations. This supports previous findings (e.g. Kogetsidis, 2024b) on the widespread use of PSMs in the non-profit sector.

A large number of applications of PSMs have focused on serious issues that many societies around the world face, such as poverty and the marginalisation of communities. Several other applications have dealt with problems of ecology, sustainability and environmental management. This however was not universal, with the results showing that Africa and Oceania – along with Europe – being the only continents in which applications of sustainability and climate-change problems were found.

A number of papers reported the use of PSMs in the areas of education and health, with fewer applications having focused on problems related to urban regeneration, defence, local government, disaster response, or other contemporary issues – examples of the latter being the departure of the UK from the European Union (Shaw et al., 2019) or how to re-invent democracy in the digital age (Laouris and Romm, 2022).

The above results have shown a very healthy record of application of PSMs that cover a wide range of important application domains. These include both areas that OR has traditionally been closely associated with, such as health and defence, but also new areas of application, such as sustainability and climate change. Furthermore, the prime focus of PSMs on the important and very complex problems that so many societies around the world face, such as poverty or the marginalisation of particular communities, remains a characteristic of the OR discipline that hasn't faded away with time. This reflects the political nature of OR and the contribution that this discipline can make as a worldbuilding discourse that shapes society.

One of the most significant findings that have come out of our study is the very global geographical coverage of application of PSMs. The study has found evidence of OR interventions that have primarily used PSMs in no less than thirty countries around the world. This might be seen as a small number in the global context but on the other hand it covers all continents and a very diverse mix of countries. The finding indicates the global nature of complex problems and highlights the continuous effort of operational researchers to provide help and support in the less advantaged parts of the world. At the same time, what is quite striking is the complete absence of papers on soft OR and PSMs published in the key US OR journals.

There are different reasons why PSMs have not been taken up by American operational researchers. One possible explanation is that the original PSMs all had British origins, with SCA starting as a joint venture between the British OR Society and the Tavistock Institute of Human Relations, and SSM being the outcome of an action research programme at the University of Lancaster. Furthermore, the groundbreaking work of Peter Checkland at Lancaster and its attack on traditional OR methodology and its “sister” approaches of systems analysis and systems engineering (Checkland, 1983) became synonymous with the new paradigm of soft systems thinking. Given the strong systemic nature of methodologies such as SSM, this domain of work soon attracted the attention of other researchers from the adjacent systems field, which also had, and still does, a much stronger representation in the United Kingdom.

Another explanation for the absence of work with PSMs in the US relates to the level of legitimacy that soft OR appears to receive across the Atlantic. This can be explained by the strong adherence by American operational researchers to functionalism – a research tradition that is concerned with an objective and concrete external reality and in which methods from the natural sciences are applied to the study of human affairs. Functionalism follows a strong positivistic epistemology and treats knowledge as being able to be easily transmitted in a tangible form. It is therefore reasonable to conclude that this “ … iron grip of positivism within operations research” (Checkland, 2006, p. 770) has affected the level of acceptance of PSMs in this part of the world and has made the pace of movement to a more interpretive paradigm, which seeks to shed light on people's different perceptions and subjective assumptions, much slower.

Maurice Kirby, who has written extensively on the history of OR, has observed that the critique of the discipline as a goal-seeking orientated analytical domain, which in the 1970s resulted in the so-called crisis in OR, has never persuaded OR practitioners or academics on the other side of the Atlantic (Kirby, 2007). For Paucar-Caceres (2011), this is rather puzzling given that the British soft OR tradition has been substantially influenced by two very important American scholars – C. West Churchman, the first editor of Management Science and Russell L. Ackoff, one of the earliest and most recognisable critics of the excesses of mathematical emphasis in the discipline. In an early article, Ackoff (1957) highlighted an important difference between the type of publications that British and American OR journals favour. In that respect, most of the papers published in Britain tend to be general discussions or case studies, rather than theoretical papers dealing with the mathematical exploration of some type of problem that arises in OR. The literature in the United States is heavily balanced in the other direction, with American OR journals clearly favouring OR that is largely “methods and techniques orientated”. This reflects the emphasis that management education and management practice in Britain place on pragmatism – the school of philosophical thought that sees knowledge derived directly from observation and therefore being practice-driven (Paucar-Caceres, 2009).

The difference in the type of publications between the two countries that Ackoff highlighted so many years ago, which still exists today, can be better understood if a simple comparison of the editorial policies of their key OR journals is made. In that respect, in Britan the Journal of the OR Society takes the view that:

On the other hand, Operations Research, the flagship journal of INFORMS – the American OR Society -, takes a very different position on what could be accepted for publication in that journal. According to their editorial policy:

The very different view taken by each of the two major OR journals in terms of what constitutes legitimate OR practice – and therefore proper scholarly work – led a group of OR academics and members of the British OR Society to send a letter to the editor of Operations Research in 2009 complaining about the fact that a recognised field of OR was systematically ignored within the US. The letter was signed by almost 50 leading OR researchers from several different countries and was published in OR/MS Today – the INFORMS members' magazine. The editor's response was simply to reiterate that for papers that are not based on rigorous mathematical modelling, the journal of Operations Research is not the appropriate outlet.

The reluctance of American OR journals to publish good academic papers which do not employ mathematical rigour has turned many researchers, who are interested primarily in issues of culture, politics and power dynamics in OR interventions, away from these journals. An implication of this is that the level of familiarity with PSMs and their subsequent adoption by OR practitioners in the country with the largest OR community in the world would be negatively affected.

In terms of the particular problem domains that our study has identified, the areas of sustainability and climate change seem to have a predominant position. Concerns about the environment and sustainable development have been a relatively recent phenomenon which reflects the accelerated level of global environmental change. Sustainability is based on the three pillars of environmental, economic and social, and sustainable development represents the effort of contemporary societies to ensure the conservation of resources. In that respect, the concept of sustainable development as a means of producing a more benign basis for human development has pervaded all aspects of life (Essex and Latouf de Oliveira Sanches, 2024). For the discipline of OR, traditional strategic, tactical and operational problems need to be revisited and studied in this new perspective in order to generate an enhanced body of knowledge that would be able to tackle the needs for a sustainable society (Santibanez Gonzalez et al., 2018). It is therefore not surprisingly that the analytical field of operation research is practically engaging with the environment and the domain of PSMs is very active in trying to find long-term solutions to sustainability problems. The dialogue between the academic fields of sustainability and PSMs has already begun to gather pace (Paucar-Caceres and Espinosa, 2011) and recent studies (e.g. Gomes Júnior et al., 2023; Kogetsidis, 2025b) have pointed out the active level of cooperation between these two important academic communities.

Our study has also highlighted the engagement of this field of analytical work with serious societal problems, such as poverty or drug trade. A key common characteristic that these problem situations tend to have is that they affect large groups of people with very limited access to resources and significantly low levels of social status, power and influence. These are important stakeholders who tend to be either underrepresented or completely absent in decision-making structures. The collaborative nature of PSMs ensures that all parties that are affected by a problem situation have the opportunity to play a part in its solution. This would require achieving the widest possible level of stakeholder participation (Aubert and Lienert, 2023) whilst at the same time respecting the norms of democratic decision-making (Brocklesby and Beall, 2018). This emphasis on the empowerment of stakeholders that are often seen to be neglected from the entire decision-making process can result in the creation of participatory bottom-up structures and will give disadvantaged groups a sense of ownership and commitment to the implementation of agreed objectives.

Given the large number of PSMs that exist today, selecting the most appropriate method for a particular situation is an important decision that needs to be made as part of the intervention process. This has been a main theme of discussion within OR and other analytical areas over the years and has resulted in putting forward the idea of methodological pluralism – i.e. using together a range of different methods and tools as part of the same intervention. Methodological pluralism can be treated by some of the advocates of particular methodologies with scepticism, given that breaking down a PSM or using only certain parts of it could weaken the methodology and damage its entire philosophy. Furthermore, it is recognised that extra care needs to be taken when a combined approach involves the use of methods and tools that come from different paradigms. In such cases, the cognitive load problems associated with individuals moving between methods and paradigms should not be underestimated.

An important challenge that PSMs will have to face is the way they deal with issues of power among the stakeholders, with critics of PSMs often attacking the “regulative” orientation that these methods have inherited from the interpretive paradigm (Jackson, 2003). The danger here is that, in OR interventions, the more powerful stakeholders might want to impose their views on others, which could result in less powerful stakeholders becoming marginalised in the intervention process. Even though some forms of marginalisation are relatively easy to overcome, others stem from conflicts that are endemic across society and are therefore much harder to change (Midgley and Rajagopalan, 2021). A way to deal with power distribution issues and the possibility of certain stakeholder groups becoming marginalised is by ensuring that a careful up-front exploration of the context of the intervention – a process that is known as boundary critique – is carried out at the early stages of the intervention (Midgley, 2000). Boundary critique can examine how stakeholders' purposes and values are intimately linked to boundary judgements and will help to determine what aspects of the problematic situation the intervention will focus on. Boundary critique can therefore transcend conflicts through dialogue and the collective exploration of different possibilities for bounding the system of concern (Sydelko et al., 2021). As such, the process of boundary critique provides an avenue for meaningful stakeholder participation in decision-making that would enable the systemic application of PSMs.

Another important challenge for PSMs is how they adapt to the digital transformation of organisational life. The emergence of new technologies, such as machine learning and artificial intelligence, has already started a new technological era with serious implications for organisations. It is not yet clear whether these unprecedented technological advances will facilitate or hinder the use of PSMs. It is also too early to say whether they might even create an existential threat to the field. There is no doubt that machines and software may refine problem representations, enhancing stakeholder understanding and serving as starting points for soft OR engagements. On the other hand, these tools may impose new constraints on stakeholder behaviour, prioritising short-term outcomes and limiting innovation (White, 2025). We share the view that decision-making is a human affair and will continue therefore to remain in the human sphere (Lami and White, 2022) but at the same time we should recognise the important impact that digital transformation and new technologies will have on the application of PSMs and the contribution that these can make. This presents an exciting new area of inter-disciplinary research in the fields of technology and social sciences, which can investigate the complex interaction between technology and people and shed more light on how the new digital society will affect human well-being.

This study has shown that the area of soft OR continues to be a popular field of scholarly work within the wider discipline of OR, with a large number of applications in different problem domains. Its use covers areas that OR has traditionally been closely associated with, such as defence, health and education, but also extends to new areas such as climate change and sustainability. This shows the adaptive nature of the discipline and its ability to evolve and to be inclusive in terms of the new complex problems and challenges the word faces. On the other hand, it is rather disappointing that this important and dynamic field does not seem to enjoy the same level of acceptance in the US, where formal OR societies and journal editors clearly treat traditional OR with its goal-seeking orientation as the only legitimate part of the discipline. Our results have confirmed that the emphasis in Europe is on the actual application of the methods and tools of OR and the dissemination of good practice through the publication of relevant practical case studies, whereas the editors of American OR journals continue to favour theoretical papers of a highly mathematical content advancing the technical side of the discipline.

A limitation of our study is that it has focused exclusively on English-speaking journals in a particular academic discipline. It is therefore recognised that the lack of representation of non-English and practitioner-led publications points to a gap in the evidence base that might bias the results. Furthermore, it should also be taken into account that the papers that are published in relevant academic journals only cover part of the actual application of PSMs, given that many of these interventions have been carried out by OR practitioners who, unlike academics, do not necessarily have the same interest or incentive in publishing their work. Although the inclusion of more sources would be expected to increase the evidence of the level of use of PSMs, this is another area that needs to be investigated further. Expanding research to include adjacent academic fields, non-English speaking journals and practitioner-led publications would not only provide a more inclusive picture of global OR practice but also strengthen the discipline's connection to real-world decision-making.

Our findings have several practical implications for the development and positioning of PSMs as an important domain of research and application. Apart from highlighting the continuing relevance and practical value of soft OR in addressing many complex global issues, the findings also point out the need for OR practitioners to become more familiar with the basic concepts, methodologies and tools of this field of scholarly work. Teaching soft OR has been recognised as being challenging and the very large number of PSMs that exist today make it difficult for these methods to be adequately included in university curricula. When they are included in academic programmes, their coverage tends to focus on one or two of the more established PSMs, such as SSM or SODA, and to be limited in time and scope. On the other hand, ignoring this important part of the discipline and training OR analysts exclusively in mathematical methods and tools without giving them an awareness of the actual realities of the organisational and management contexts is thought to do them a huge disservice (Mingers, 2011).

At the same time, it is also crucial that OR practitioners prioritise the development of their soft and facilitation skills. Including soft OR themes in university programmes and teaching PSMs effectively require both modelling skills and process skills (Ackermann, 2019). As these types of skills cannot easily be taught by standard textbooks, it is imperative that future generations of operational researchers are equipped with a more balanced set of both technical and interpersonal skills. Universities and OR societies around the world certainly have a big role to play in this.

Another practical implication of our findings is that there is a need for a more intense dialogue between the different research traditions, as these are expressed in different parts of the world. There is no doubt that the value of PSMs in dealing with the important political, cultural or other complex dimensions of organisational problems will be recognised further if the editors of American OR journals revise their editorial policies and extent the scope of their journals to include high quality papers on the contribution and further development of soft OR and PSMs. Encouraging more cooperation between European and American OR societies, as well as building further international collaboration among OR academics and practitioners, will help the entire discipline make a more important contribution in dealing with the world's grand challenges.

We remain optimistic that facilitated modelling and PSMs have a bright future and a significant contribution to make. As the world continues to face many unsolved problems and new complex challenges, the discipline of OR and the domain of PSMs still have a lot to offer.