Reviewing and revising Black et al’s adjustment model(s)

Abstract Previous reviews of Black et al’s expatriation and repatriation adjustment models have evaluated the influence and reliability of the models. In this paper, we examine the changing and varied nature of engagement with the models in journal articles on international adjustment to investigate the implications of contemporary changes among expatriates and their behaviours and experiences. 699 peer-reviewed academic articles published between 1991 and 2021 were systematically reviewed. Our analysis reveals that while more than 80% of the articles referenced their model(s), only a third explicitly applied the model(s). Drawing on our findings, we advance a revised version of Black et al’s conceptual framework, which integrates their models into a combined stage-adjustment model applicable to both assigned expatriates (AEs) and non-assigned expatriates (NAEs).


Introduction
Expatriation research continues to grow as a field of management inquiry, with international experience being an increasing focus of interest as a key contributor to the competitive advantage of individuals and organisations (Kraimer et al., 2016;Suutari et al., 2018).Expatriation is commonly viewed as a process comprising three stages: pre-expatriation, expatriation, and repatriation (Cerdin & Pargneux, 2009).Pre-expatriation typically focuses on an individual's motivations for an international assignment and preparations for it.The expatriation stage engages with experiences of living and working abroad, and repatriation covers the return to the home country.These transitions require expatriates to undertake profound cognitive, psychological, and behavioural changes to successfully adjust to their new environments (Bhaskar-Shrinivas et al., 2005), thus making international adjustment the focus of expatriation and repatriation research (Andersen, 2021).
Black and his colleagues conceptualise international adjustment as both multifaceted (work and general adjustments together with interactions with host-country nationals) and time-related (anticipatory and in-country adjustments) (Black & Stephens, 1989;Black et al., 1992).Based on the integration of uncertainty reduction theory and cross-cultural theories (Black, 1988;Church, 1982;Torbiörn, 1982), Black et al's expatriation (Black et al., 1991) and repatriation (Black et al., 1992) adjustment models suggest that expatriates can reduce the stress caused by the unknowns of living and working abroad by formulating expectations and preparing themselves accordingly.The more accurate their expectations, the more likely they will be able to tackle the challenges of expatriation, thus supporting their psychological well-being (Black & Gregersen, 1991;Black et al., 1991).
Since the publication of Black et al's model(s), scholars have cited their adjustment model(s) more than 3,000 times according to Google Scholar as of November 2023.This high number of citations serves to exemplify the long-lasting influence of the model(s), which have been applied across a variety of geographical settings (Bhaskar-Shrinivas et al., 2005;Hechanova et al., 2003).Although several conceptual articles have emphasised the strengths of the model(s), others have highlighted their limitations (Haslberger et al., 2013;Hippler et al., 2014;Lazarova & Thomas, 2012), leading to calls for the development of new and alternative approaches to the examination of international adjustment (Dabic et al., 2015;Takeuchi, 2010).What has not been investigated yet is how contemporary changes in the expatriation population, such as the increasing recognition of non-traditional forms of expatriation (Hutchings, 2022;McNulty & Hutchings, 2016) challenge the underlying assumptions of the models and prompt the need for a revised stage-adjustment model.
We address this gap by investigating the following research questions.How have expatriation and repatriation articles published between 1991 and 2021 engaged with Black et al's adjustment models, and how and why has this engagement changed and varied?Drawing on this analysis, what revisions to the stage-adjustment framework are needed?
Our review begins by presenting Black et al's expatriation (1991) and repatriation (1992) models.After which, we explain our review methodology.We then examine levels of engagement with the models across 699 articles and present our analysis of three key themes: (i) the multifaceted nature of the models; (ii) multi-stakeholder perspectives; and (iii) increasing recognition of the diversity of expatriates.We use these findings to contribute to the development of a combined stage-adjustment model, which encompasses assigned expatriates (AEs) and non-assigned expatriates (NAEs) and moves beyond the existing focus on expatriation or/and repatriation.This is followed by a discussion of the theoretical and practical implications of our review for future research on expatriation and repatriation adjustment and practice.

Black et al's expatriation and repatriation adjustment models
This review examines two models created by Black and his co-authors.Their expatriation adjustment model (Black et al. 1991) and their repatriation adjustment model (Black et al. 1992).Both models shown in Figure 1 below share the same empirical and theoretical foundations.The arrows illustrate the expected linear journey of expatriates, from  (Black et al. 1991) and repatriation (Black et al. 1992) adjustment models.
their anticipatory adjustment at home, to their adjustment in their host country, followed by their return to their home country.
Black and his co-authors first introduced their expatriation adjustment model in 1991 building on their research on American managers sent to Japan, Hong-Kong, Korea, and Taiwan.Their adjustment model was based on growing recognition of international culture shocks (Oberg, 1960) and control theories to extend the study of work adjustment and transitions to international mobility (Louis, 1980;Sánchez Vidal et al., 2010).Integrating the contributions made by these streams of literature led to the redefinition of cross-cultural adjustment as both multi-faceted and staged with the introduction of anticipatory and in-country adjustment stages (Black & Stephens, 1989).The model allowed the identification of antecedents to adjustment outcomes across time (anticipatory and in-country) and space (home and host-country) in both work and non-work areas.
Although primarily based on empirical evidence, the theoretical roots of the model(s) stem from stress theories and the principle of uncertainty reduction where accurate expectations prior to departure promote individual psychological comfort once in the host-country (Black & Gregersen, 1991;Black et al., 1992).Being able to assimilate and fit-in with their new environment requires individuals to learn appropriate codes and routines in-and out-side of work to regain control and reduce stress (Bandura, 1977;Black et al., 1991).The two stages (anticipatory and in-country adjustment) along with the antecedents and facets of adjustment (work, interaction and general adjustment) were later used to create the repatriation adjustment model (Black et al., 1992).This staged view of international adjustment and their models have become the most applied models in both expatriation and repatriation management research (Andersen, 2021;Chiang et al., 2018;Knocke & Schuster, 2017).

Methodology
We conducted a systematic literature review (SLR) in line with our aim of thoroughly reviewing and assessing engagement with their model(s) in expatriation and repatriation adjustment articles.Systematic reviews enable a transparent and replicable analysis of relevant existing literature (Fink, 2005;Post et al., 2020).They start with clear research questions and objectives upon which is based a search strategy (e.g.searching strings, inclusion and exclusion criteria).The evidence collected is systematically reviewed and presented with the aim of minimising bias and enhancing reliability (Shamseer et al., 2015).
Specifically, we drew on the strengths of mixed-methods systematic literature reviews (Hong et al., 2017;Stern et al., 2020) to bring together articles investigating the antecedents and outcomes of adjustment (quantitative studies) with those (also) concerned with expatriates' experiences (qualitative studies and mixed-methods designs).In line with the preferred reporting items for systematic reviews and meta-analysis guidelines (i.e.PRISMA guidelines), our eligibility criteria, search strategy, selection process, and method of analysis are detailed as follows.First, we restricted our search to peer-reviewed academic articles published in the field of management to establish relevant disciplinary parameters.Our focus on peer-reviewed published academic articles led us to exclude special issue introductions, conference proceedings, book reviews and chapters, and student theses.Second, using three of the largest and most sophisticated electronic databases (EBSCOhost, ProQuest, Emerald), along with the library catalogue of a UK university powered by Sierra, we searched for articles containing the words 'adjustment' , 'expat*' , 'repat*' , 'return' , and 'assign*' in their titles and abstracts.The selected time frame was January 1991 to December 2021 to cover over 30 years of development in research and theory on expatriation and repatriation adjustment.Third, we focused on assigned expatriates (AEs) and non-assigned expatriates (NAEs), examples of which would include self-expatriates, who are individuals temporarily relocating overseas without the support of a sending organisation (Inkson et al., 1997;Richardson & McKenna, 2002), and short-term expatriates, who are parent country nationals (PCNs) assigned to international postings for short periods of time, usually shorter than 6 months (Collings et al., 2007;Shaffer et al., 2012).We also included flexpatriates and international business travellers (IBTs) (i.e.AEs undertaking frequent international business trips without relocating in the host country) in our sample (Mayerhofer et al., 2004;Welch et al., 2007).
We define AEs as PCNs sent from the home country of multinational companies (MNCs) to foreign subsidiaries (Black et al., 1991).Doing so, we distinguish them from inpatriates (i.e.employees recruited from a MNC's subsidiary or a third country to work in the MNC's headquarters), transpatriates (i.e.employees from a foreign subsidiary assigned to another foreign subsidiary) and virtual expatriates (i.e.employees with international responsibilities who do not physically relocate to a host country (Harvey et al., 2011;Welch et al., 2003;Arp et al., 2013).
We define NAEs as individuals who initiated their relocation, with the intention of gaining regular employment during temporary stay in a foreign country (Cerdin and Selmer, 2014).Thus, we excluded students, tourists, dependants of expatriates and migrants from our sample.We do not consider academic or professional qualification as a necessary criteria to be categorise as an expatriate to include non-degree holding and low-skilled/low-status expatriates (e.g.religious and humanitarian underpinnings (where explicitly stated).In the case of the empirical articles, we also recorded their research methods and data collection tools along with the characteristics of the samples studied when available (types and functions of expatriates and their home and host countries).
Additionally, the studies reported in the articles were categorized based on their level of engagement with the model(s) of Black et al.To do so, the team first undertook a word search for the term 'black' in the full text of all 699 articles to gain insight into the number of times the articles cited the model(s).The literature sections of the articles were read, and their reference lists were reviewed.As such, we can only account for articles that explicitly mentioned the model(s) within their text and references.Detailed notes were taken on a sub-sample of 370 of the 699 articles (examples of which are available in Table 2).Second, the research team examined how this sub-sample of articles engaged with key features of the models: (a) the definition of adjustment as being related to the degree of psychological comfort anchored by uncertainty reduction theory (Church, 1982); (b) the acknowledgement of adjustment as a multidimensional concept; and (c) the recognition of its temporal dimension with a distinction between anticipatory and in-country adjustment.Finally, the comparison between our notes and these criteria led to the development of a three-point coding scheme ranging from the application of the model(s) to not mentioning the model(s) at all.Articles coded in the application category are those who both applied and referenced the model(s) to answer their research questions and objective(s).On the other hand, articles in the citation category only referenced the model(s) without theoretically and/or empirically engaging with the model(s).Finally, articles in the no mention category did not refer to or engage with the model(s) in the main body of the articles.Further explanation along with details of the articles in each category and the application of our coding scheme can be viewed in Table 2. Content analysis was conducted to synthesise the information collected from the articles.Where possible, the descriptive data collected for each article was transformed into a code and combined with the level of engagement with the model(s) in each article.For instance, the chosen stage of expatriation was coded from 1 to 4, where 1 covered the pre-expatriation stage and 4 covered articles investigating pre-expatriation, expatriation, and repatriation.Lastly, we undertook a thematic analysis to identify and analyse the key themes in the categories identified (application, citation, and no mention).
Throughout the conduct of the SLR (2020-23), all three authors discussed and reviewed the coding regularly during the initial stages of each search.This was done to agree on the research protocols (e.g.exclusion and inclusion criteria) and collectively resolve any issue encountered at the search level (e.g.access issues) or with the coding of a particular article.The research team then met on a bi-monthly to monthly basis to discuss the initial findings to ensure consistency and counteract personal subjective biases.Finally, the preliminary findings were collaboratively assessed before undertaking a full analysis of the literature base in keeping with our research questions.

Findings
The findings from our coding analysis by level of engagement are illustrated in Figure 2. Research on expatriation and repatriation adjustment steadily increased in the 1990s.Since the 2000s, the number of publications increased substantially, with an average of 24 articles published per year between 2000 and 2010 and 33 between 2011 and 2021.In line with previously published reviews, our findings suggest a connection between the number of publications in the field and global economic cycles (Dabic et al., 2015;McNulty & Selmer, 2017), as illustrated by two sharp decreases in publication outputs following the financial crisis of 2008 and the COVID-19 pandemic.
Figure 2 also illustrates a close relationship between the number of articles published (line 1) and the number of articles referencing the model(s) (line 2).This is supported by the results from our engagement coding scheme (Table 2), with more than 80% of the articles in the sample reference the stage adjustment model(s), as reported in the methods section above.However, while the two lines almost overlap until 2012, they start to diverge afterwards.This suggests that while the model(s) remain the most cited in the field, engagement with the model(s) has changed over recent years.In addition, the number of articles referencing the model(s) (line 2) greatly differs from the number of articles applying the model(s) (line 3).This is because although a large number and percentage of articles mention the model(s) (n = 573, 82%), only a minority of them actually build on the model(s) through the results or findings of their study (n = 239, 34%).This is supported by specific changes in the distribution of articles in our sample within three categories based on their level of engagement with the model(s) (Figure 3).We divided the 31 years of publications represented in our sample into three periods: the 1990s, the 2000s, and 2010 to 2021.While the percentage of articles referencing the model(s) has remained high, the gap between the number of articles referencing the model(s) and those applying the model(s) has grown since 2011.On the other hand, the number of articles not mentioning the model(s) doubled after 2010 compared to the previous two decades (24% of the total number of articles present in our sample between 2011 and 2021 compared to 12% and 11% in the 1990s and 2000s, respectively).Having demonstrated changing levels of engagement with the model(s), the following sections focus on the key theme for each category: the multifaceted nature of the model(s) for articles applying the model(s), the adoption of a multiple stakeholder approach for articles citing the model(s), and the recognition of the diversification of the expatriate population for articles not mentioning the model(s).The aim is to highlight how changing trends and patterns in international adjustment research either add to or expose some of the limitations of the model(s) and to identify the relevant changes needed.

The multifaceted nature of the model(s)
Articles applying the model(s) did so to analyse the anticipatory and in-country adjustment of expatriates during their international transitions (i.e.expatriation and repatriation).These articles constituted a third of our review sample and predominantly focused on the adjustment of AEs.A minority of the studies applied the model(s) to NAEs or mixed samples of AEs and NAEs.In line with the empirical roots of the models, the main focus is on the expatriate and the role played by sending organisations in supporting their adjustment.

Pre-expatriation
We found twenty articles examining the relationship between anticipatory adjustment and expatriation adjustment using Black et al's adjustment model(s).These articles focused on the selection and training of AEs, which are both antecedents of adjustment in the expatriation model.As for selection, Selmer (2001) empirically verified the part played by personal characteristics such as age and marital status in affecting all three dimensions of adjustment.This is in line with articles highlighting the role played by one's demographic characteristics and life cycle on motivations to expatriate and subsequent adjustment (Lazarova et al., 2010;Naithani & Jha, 2009).For instance, with the dual-career model becoming more common, organisations are now encouraged to consider the interruptions caused to a spouse's career created by an international posting to identify a strategic window to assign employees overseas (Dickmann et al., 2008).As for the topic of expatriate training, Koo Moon et al. (2012) enriched our understanding of pre-departure training by highlighting the role played by cultural intelligence and previous international experience in the effectiveness of organisational training, thus stressing the need to recognise an expatriate's soft skills such as emotional intelligence or cross-cultural abilities during the selection stage (Gabel-Shemueli & Dolan, 2011;Susanto & Rostiani, 2012).
These studies are important as they highlight the active role played by an organisation in selecting employees during the pre-expatriation stage.However, studies have also emphasized that employees do not simply wait to be sent away or accept a posting.Feeling compelled to accept an international posting has been found to have a negative impact on the adjustment of expatriates and their work engagement (Pinto et al., 2012).A way to better align organisational practices with expatriation expectations is to recognise the role played by proactive behaviours at this stage.According to protean career theory, self-directed and value driven initiatives such as seeking additional training and opportunities outside of the workplace can have a significant impact on one's career (Hall et al., 2018;Ng et al., 2005).As a result, we contend that self-directed training and self-selection should be added to the individual antecedents and the work and career factors identified in Black et al's model(s).

Expatriation
In-country expatriation was the most studied stage of international adjustment (164 out of 239 articles of studies applying the model(s)) and principally consisted of general descriptions of expatriates' experiences aboard.Cultural distance is the main focus of investigation because of its implications for work adjustment, with less attention paid to how this affects in-country interactional and general adjustment.
Most studies focus on cross-cultural distance or cultural novelty through international comparison.The cultural distance hypothesis, on which the model(s) draw upon using the concept of cultural novelty, posits that the wider the gap between home-and host-country cultures, the greater the challenge for expatriates once abroad (Black et al., 1991;Hemmasi & Downes, 2013).Cultural distance was found to influence the effectiveness of pre-departure and post-arrival cross-cultural training due to the difficulty in adequately predicting and preparing for radical changes (Stahl & Caligiuri, 2005;Waxin & Panaccio, 2005).Yet, studies have also found that other factors such as the direction of the assignment (Selmer et al., 2007;Zhang, 2013) and perceived host ethnocentrism (Florkowski & Fogel, 1999) play a decisive role in their cross-cultural adjustment.For example, it is not unreasonable to assume that an American moving to China will encounter different challenges to a Chinese national moving to the USA based on the cultural and institutional characteristics and dynamics of these countries.This challenges the static view of cultural distance indicated in Black et al's model by highlighting the role played by an expatriate's evolving perceptions of their home and host country on their adjustment (Schneider & Asakawa, 1995).Thus, an expatriate's evolving perceptions and experiences of cultural and national institutional dynamics and those of their family and significant others need to be incorporated into the stage-adjustment framework.
Additionally, studies examining in-country adjustment emphasize the role played by perceived organisational support (Kawai & Strange, 2014;Takeuchi et al., 2009) job characteristics (Kittler et al., 2011;Takeuchi et al., 2008) and individual skills and abilities such as cultural intelligence, emotional intelligence or personality (Chen et al., 2010;Gabel-Shemueli & Dolan, 2011) on work adjustment and performance.Specifically, individuals who were motivated by the pursuit of an international career were more likely to adjust successfully to life overseas due to the alignment between their career goals and the international posting (Haslberger et al., 2013;Selmer et al., 2003;Wang & Takeuchi, 2007).Building on motivational theory, studies have shown that finding purpose in the time spent abroad lead to increased intrinsic motivation and greater psychological well-being as expatriates perceived their assignment to be a developmental opportunity (Ramaswami et al., 2016;Selmer, 2000).These studies add to the original model by acknowledging the role played by one's motivation to learn, a crucial part of Bandura's learning theory upon which the model draws upon (Bandura, 1977;Black et al., 1991).In line with our point above on pro-active attitudes, we suggest that an individual's motivation to adjust should be added to recognise the distinction between one's ability (i.e.individual skills and organisational support) and one's motivation to adjust during their expatriation.

Repatriation
We found 42 articles building on Black et al's model(s) to examine the cultural adjustment of repatriates.In addition to the application of the model(s) to different cultural settings, the main focus has been on the turn-over of AEs and the career growth of repatriates with the aim of providing recommendations for HRM practice.
Drawing on human capital theory and career capital theory, studies have shown that international experience can become a source of competitive advantage for individuals translating into future perceived and objective career successes (Benson & Pattie, 2008;Biemann & Braakmann, 2013, Cerdin & Pargneux, 2009).Ramaswami, Carter and Dreher (2016) found expatriates who undertook multiple assignments in upper managerial positions were more likely to achieve higher levels of compensation.This is in line with the human capital theory where exposure to a new environment allows individuals to acquire international skills and competences, which offer them a source of competitive advantage (Stevens et al., 2006).Yet, studies have highlighted that repatriates are unlikely to be satisfied with their positions when returning to the country they left (Sánchez Vidal et al., 2010), typically due to a lack of perceived clear internal opportunities to use the skills, knowledge and abilities developed abroad (Oddou et al., 2009;Stahl et al., 2009).This mismatch between their ability and their positions upon return leads to a lack of perceived fit between their new position and their career expectations and can hinder their motivation to act as 'knowledge transferrers' (Bonache & Zárraga-Oberty, 2008).
In addition, a mismatch between their career expectations and the reality of their position back home can be perceived as a psychological contract, thus increasing their intention to leave their employer (Black et al., 1992;Ren et al., 2013).Using hope theory, Zikic et al. (2006) emphasize the agentic views held by repatriates where the inability of their employing organisation to meet their career goals motivates them to seek external opportunities.Repatriates are more likely to do this if the confidence built by a successful adjustment to working abroad is perceived as a personal success (Benson & Pattie, 2008;Suutari & Brewster, 2003).In line with modern career theories, alignment between individual positions at home and their individual career plans need to be added to the work and career dimensions of the model(s).
Finally, thanks to the advances in technology, individuals now have greater access to information about their home-country while abroad.Ellis et al. (2020) reported the positive role played by new communication technology on the ability of individuals to form accurate expectations of their experience of returning home.Therefore, we argue the model(s) need to be updated by adding the 'nature and frequency of communication' as one of the individual antecedents to repatriation adjustment.This is because it is not only an expatriate's physical reality (time overseas and visits home) which impacts their future repatriation adjustment, but also their ability to maintain relationships and obtain information through communication technologies.

The multi-stakeholder perspective
The studies citing but not applying the model(s) accounted for almost half of the review sample.While the focus of attention was on expatriates and their sending organisations for the studies applying the 1991 model, the studies here emphasized the role played by other parties in the adjustment of expatriates and repatriates such as host-country nationals, communities, family and significant others.We suggest this could explain why these studies acknowledge the seminal role played by Black and his colleagues in defining cross-cultural adjustment without empirically or critically engaging with the model(s).

Family and spouse adjustment
Although the adjustment of accompanying family members is recognised in Black et al's models (Black et al., 1991(Black et al., , 1992)), many articles emphasize how changes in careers and family dynamics warrant necessary adjustments to the models.For example, the increasing prevalence of dual-career relationships where both partners are employed underlines the career disruptions incurred by trailing spouses through international postings that could lead to heightened marital stress and maladjustment in expatriates ' work and non-work adjustment (Caligiuri et al., 1998;Gudmundsdottir et al., 2019;Harvey, 1996;McNulty, 2012).While their maladjustment is often considered a prime reason for expatriation failure, Selmer and Lauring (2010) and Schütter and Boerner (2013) suggest a more reciprocal relationship between work and family domains than assumed in Black et al's model(s) where positive interactions between the two can support expatriation success.
New forms of international postings such as the use of short-term assignments could help alleviate the stress placed on an expatriate's family by avoiding the physical relocation of family members (Konopaske et al., 2009).However, short-term assignments are not without their own challenges with international assignees being less able to draw comfort from the support of their loved ones while abroad and more likely to experience difficulty when dealing with the disruptions created by these assignments on their family routines (Starr & Currie, 2009).This study also found that not only married expatriates have family concerns.Therefore, to better account for the diversity of relationship statuses and family dynamics, we suggest replacing 'spouse and family adjustment' with 'family and significant others work and non-work adjustment' to highlight the effect of personal relationships in the process of adjustment.

Host-country nationals
A growing body of literature recognises the role played by host-country nationals (HCNs) as active members of the adjustment process.Expatriates' social networks can have a positive influence on their psychological well-being by offering them access to knowledge and information with regard to life in their host-country (Pustovit, 2020;Wang & Kanungo, 2004, Yamao et al., 2020).Several factors influencing the quality of the relationship between expatriates and HCNs have been investigated, such as the language and reflective skills of an expatriate (Bala Kuki et al., 2021;Molinsky, 2007;Zhang & Peltokorpi, 2016), the quality and frequency of cross-cultural interactions (van Bakel, 2019), and an expatriate's attitudes toward HCNs such a tendency towards ethnocentrism and lack of cultural humility (Caligiuri et al., 2016;Lai & Yang, 2017).According to social categorisation theory (Tajfel & Turner, 1986), both expatriates and HCNs are likely to categorise each other as members of an out-group, thus restricting their motivation to connect and share meaningful information (Sonesh & DeNisi, 2016).Uncooperative behaviours are expected to arise when existing HRM practices antagonise differences between expatriates and their local colleagues in the host-country.For example, in relation to pay and benefits (Toh & DeNisi, 2005) or ignoring the cultural characteristics of the host country (Sokro & Moeti-Lysson, 2018).As a consequence, an expatriate's relational and perceptive skills are not enough to guarantee positive interaction adjustment as assumed in the 1991 model.We argue the skills and motivation to interact with individuals are important among host country nationals as well as expatriates.Thus, we add the support from host country nationals as a new contextual variable to the models.

The role played by social communities
Although the critical approach adopted in these articles deepen our understanding of the agentic role played by HCNs in the adjustment of expatriates, future research should also extend its field of inquiry beyond an expatriate's local colleagues.This would lead to recognition of friends and social communities as important actors in the cross-cultural adjustment of expatriates.In Black et al. (1991) model, socialisation strategies are initiated and sustained by the sending organisation.However, we also identified four studies emphasising the role played by social interactions outside of the work-sphere on the cross-cultural adjustment of expatriates.Lauring and Selmer (2009) provide ethnographic evidence that expatriate communities such as those existing within gated communities play a pivotal role in the adjustment of assigned-expatriates by offering help and support to fellow expatriates while minimising or excluding exposure to the host-country's local culture (e.g.not having to learn the host-country's language to socialise).Within these secluded communities, adjusting to life abroad may require limited interaction with HCNs or familiarisation with the host-country.On the other hand, van Bakel et al. ( 2017) emphasise the benefits associated with the paring of expatriates with a local host with whom the expatriate could socialise with outside of the workplace.These friendships provided four types of social support: social companionship, informational, emotional and informational support, contributing to the social capital of expatriates and by extension their adjustment.Therefore, we suggest that expatriates do not solely rely on their sending organisation to satisfy their need to belong while abroad (Yunlu et al., 2018), and that the model(s) should be adjusted to account for expatriates' ability and motivation to utilise their social capital to aid their adjustment.

Recognition of the increasing diversity of the expatriate population
Articles not referencing the model were characterised by their recognition of the increased diversity of expatriates.Within our sample, the number of articles not mentioning Black et al's model(s) while investigating expatriation and repatriation adjustment doubled after 2010 compared to the previous two decades.To better understand how the expatriate population is changing and identify relevant changes to the model(s), we looked at NAEs and non-traditional AEs.Finally, we briefly highlight the role played by critical incidents on cross-cultural adjustment before identifying links between the changes suggested for each key theme.
Studies on NAEs often build on mixed samples in terms of the levels of responsibility held by their participants, their required expertise, and sector of activity, which present an obstacle to our ability to build occupation-specific patterns of adjustment.However, the investigation of NAEs helps to gain a deeper understanding of the ways in which non-assigned expatriation democratises access to international experiences for individuals who are less likely to be selected for assigned expatriation, such as younger or less experienced professionals (Andresen et al., 2015;Guttormsen & Francesco, 2019).This diverges from Black et al's original models, which focus on the specific characteristics of the role on expatriation and repatriation adjustment (role clarity, discretion, novelty and conflict) rather than an individual's career and work expectations.Andresen et al. (2015) found that non-assigned expatriates were likely to possess lower levels of social capital than their assigned counterparts, leading them to accept a less skilled or senior job abroad.This may be due to a lack of financial support where NAEs rely on their savings to sustain their life abroad while securing a paid position (Inkson et al., 1997).As such, it is not only one's social capital that can impact the in-country adjustment of NAEs but also their financial resources, a factor that is not currently addressed in the models because these matters are taken care of by a sending organisation.Additionally, while their time abroad offers a great opportunity for them to acquire new forms of human capital, this capital can be more difficult to transfer once back in the home-country (Begley et al., 2008;Guo et al., 2013).These studies highlight the receptivity of organisations to 'new' knowledge, which is assumed to be positive in the model(s).This is because AEs were sent to foreign subsidiaries of multi-national companies, thus sharing a common interest and objectives.However, this is not the case in studies focusing in NAEs who have to find employment independently.Therefore, we suggest that the degree to which a recruiting organisation is (inter)nationalised (both at home and abroad) will influence the organisational support received by NAEs, with organisations making a conscious effort to welcome NAEs being more likely to attract and retain a satisfied international workforce (Chen & Shaffer, 2017;Jonasson et al., 2018).

Non-traditional forms of assigned expatriation
We found 11 articles focusing on new forms of assigned expatriation, such as short-term assignments, commuters, and frequent flyers.Of the issues of interest within our review were their well-being and work-life balance (Mayerhofer et al., 2011;Rattrie & Kittler, 2020), their career management (Mayerhofer et al., 2004;Starr & Currie, 2009), and the management of their performance (Tahvanainen et al., 2005;Welch et al., 2007).For example, Kang et al. (2016) suggest that while the use of short-term assignments can help to offer the flexibility needed to achieve internationalisation goals, little is known in regard to the effective selection and training of these expatriates.Indeed, non-traditional AEs are less likely to experience all three stages (pre-expatriation, expatriation, and repatriation) because of the temporary nature of their relocation (Dimitrova et al., 2020;Shaffer et al., 2012).Intrinsically, the flexibility of these new forms of assignments questions the relevance, order and content of each stage of the model(s), because a growing number of companies plan to use short-term assignments and commuter arrangements as alternatives to expatriation (Atlas, 2022).
Additionally, Andresen et al. (2015) argue that boundaryless careers, which exist outside the boundaries of a single organisations (Hall, 1996(Hall, , 2002)), are not exclusively the domain of NAE.AEs also have the opportunity to initiate international career transitions.This is in line with McNulty & Vance's (2017) argument that the careers of expatriates have evolved between assigned and non-assigned expatriation to suggest eight types of expatriates as opposed to two (assigned expatriates versus self-initiated expatriates).This argument echoes our limited understanding of potential changes to expatriation status and the impact of these changes on cross-cultural adjustment.For example, when an AE decides to remain in the host-country by accepting a position in a local company or takes up a succession of short-term international postings as an international business traveller or commuter.To account for these alternatives to expatriation and repatriation, we suggest adding remaining in the host country and re-expatriation as alternatives to the repatriation stage in Black et al's model(s).

The role played by critical incidents
Finally, we found articles acknowledging the role of external factors not encompassed in the model(s), such as economic, political or personal shocks in an expatriate's anticipatory and in-country adjustment.For example, Richardson and McKenna (2002) proposed 'refugee' as one of the four types of self-initiated expatriates to account for individuals having initiated their expatriation to escape adverse economic conditions in their home-country.This is likely to have an initial negative influence on their adjustment as their expatriation was led by a need to escape a negative environment (Selmer & Lauring, 2013, González et al., 2021).As such, these incidents can happen at micro (e.g.ill-health, a relationship breakdown), meso (e.g.changes at an organisational or sectoral level), and macro levels (e.g. an economic recession) and influence one's decision to leave, their adjustment in the host-country and their decision to return home as exemplified by the emergency repatriation of thousands of expatriated workers at the height of the COVID-19 pandemic.Therefore, critical incidents at different levels should be added to the list of contextual variables influencing in-country adjustment.

Possible interconnections
Many of the changes in each of the three sections above would apply to more than one type of expatriates.For instance, changes in expatriation status can affect both NAEs and AEs, especially as NAEs tend to stay longer than AEs, report higher levels of interaction with HCNs while also being younger and single (Dickmann & Doherty, 2008;Nolan & Morley, 2014).This relates to their level of embeddedness or life enrichment while abroad as recognised through the adoption of a multiple stakeholder perspective, when life changes such as meeting significant others or starting a family influence their adjustment.To give a final example, the recognition of individual proactivity in gathering information related to their future host-country or building new networks while abroad is applicable to both AEs and NAEs.Therefore, we align ourselves with the view that AEs and NAEs have more in common than is often assumed, a perspective shared by the authors of the eight articles in our sample having applied the model(s) to NAEs to investigate their adjustment in Denmark, Sweden (Selmer & Lauring, 2011), South Korea (Froese, 2012), and the UAE (Isakovic & Forseth-Whitman, 2013) and their repatriation adjustment in New Zealand (Ellis et al., 2020).

Discussion
Our review confirms that Black et al's models are still widely relevant, with more than 80% of the articles in our sample drawing on it to guide their research endeavours.However, the decreasing number of studies engaging with the model(s) in the last decade exposes several limitations to the model(s), which can be addressed through the revision of the model(s).Articles applying the model(s) largely focused on AEs and helped illuminate how self-determined or proactive career behaviours challenge the original assumption of career linearity (i.e.where one gets chosen for an assignment, expatriates, and returns to a more senior position).Articles only citing the model(s) were more likely to do so as they paid interest to other actors 'around' the expatriate to contest an expatriate-centric view of adjustment.Finally, those that did not mention the model(s) investigated expatriate populations so different from the original sample of Black et al. that their primary focus was on the collection of rich, qualitative data rather than theory application and development.Despite their different levels of engagement with the model(s), there is a need for a revised integrated model, which we present in the following section before discussing the practical contributions of our review.

Theoretical contributions
Our theoretical contributions come through the integration of the models into a combined and revised stage-adjustment model encompassing both expatriation and repatriation antecedents and factors.The revised model is shown in Figure 4 with changes to the model shown in italics.Based on our findings, we propose the adjustment of some of the components of the model (e.g.replacing 'spouse' with 'significant others') and the addition of new ones such as the role played by critical incidents at one or more levels in expatriation and repatriation adjustment.In addition, we propose the addition of re-expatriation as an alternative to repatriation to recognise that  (Black et al. 1991(Black et al. , 1992)).
assignments may not necessarily be preceded by anticipatory adjustment nor followed by repatriation.The revised model also includes the possibility for expatriates to remain in their host-country, for instance through citizenship and/or permanent residency.

Practical implications
The focus of existing international adjustment research has been on the management of AEs with a strong emphasis on some of the negative aspects of the process such as the cost of expatriation failure or the high attrition rate of assigned expatriates.Changes in the characteristics of expatriates can provide opportunities for firms and individuals.Non-assigned expatriation can democratise access to international experience to individuals less likely to be selected for assigned expatriation, such as women and younger or less experienced professionals (Andresen et al. 2015;Guttormsen & Francesco, 2019).For organisations at home and abroad, recruiting self-expatriates and repatriates could allow them to cut costs by using them as a substitute for company assigned expatriation (Kumar, 2019).This would represent a promising opportunity for firms of all sizes to make the most of an otherwise relatively under-tapped pool of global talent available domestically (Carpenter et al., 2001).Furthermore, one of the main findings of this SLR was the role played by modern working arrangements in shaping both assigned and non-assigned expatriate profiles and career paths.Adopting our adapted model (Figure 4), could enhance alignment between the original model(s) and the current dynamics of the field.

Limitations
Our review focused solely on expatriation and repatriation adjustment research, excluding other mobile individuals such as students, sojourners, or migrants who may have been or become expatriates.This prevents drawing conclusions beyond the specific issue of adjustment.Other important issues have been neglected here, such as the adjustment of inpatriates or the recent development of virtual expatriates, to provide a few cases.Our choice of search words could have excluded individuals relevant to our population of study by using labels that do not contain the root term of 'expat' or 'assign' .Examples of such labels which we later identified and included in our sample are global careerists, international business travellers, and frequent flyers.Reviewing peer-reviewed journal articles excludes insights from other publication types, such as books or conference proceedings.Restricting our search to articles published in English could have hindered the exploration of contextual and regional differences in international adjustment.Ultimately, the application of our coding scheme was based on the theoretical underpinnings explicitly stated in the articles, meaning that subtle or obvert references may have been missed.Given the qualitative nature of this review, the interpretation of our coding scheme is subjective.Finally, prior studies mentioned in our review critique the underlying theories and components of the model(s), possibly contributing to their decreased use alongside changes in the expatriate population and context.Despite these limitations, we hope our review inspires researchers to go beyond the apparent dominance of a model or theory in future research endeavours.

Conclusions
Adjustment remains the most studied topic in expatriation and repatriation research for its role played in improving company performance.Our review contributes to the international adjustment literature in several ways.First, by investigating engagement with the Black et al's adjustment models, we debunk the assumed relationship between citation and theoretical engagement.Second, we highlight changing trends and patterns in expatriation and repatriation adjustment studies.Third, we build on these findings to advance a revised and integrated stage-adjustment model better suited to the current realities of international (re)adjustment.

Figure 2 .
Figure 2. n of articles by publication year along with the number referencing and applying Black et al's model(s).

Figure 3 .
Figure 3. changes in the level of engagement with the model(s).

Table 1 .
The screening process.

Table 2 .
The coding scale.
made in the text.There is a reference to Bhaskar-shrinivas et al. 's meta-analysis in the introduction to support an increased focus on expatriation research.