Staying and immobility: new concepts in population geography? A literature review

Abstract. Immobile populations have received academic attention in recent years, following a period of focus on hypermobility and increasing migration as the main research interest. This article analyses the existing stock of literature on the topics of “immobilities” and “staying” to give insight into the importance of these concepts for rethinking contemporary population geography. It considers texts dealing with voluntary and involuntary types of immobility, as well as reasons for and factors influencing the increased observed immobility in the context of internal migration. Common theoretical frameworks used to explain immobilities and consequences for increasingly rooted societies are discussed. The paper also presents open research questions for future research. It draws the conclusion that staying and immobility are meaningful concepts for future research in the context of population and human geography, since they introduce a new perspective for research dedicated to spatial living patterns of populations. These concepts furthermore highlight the importance of different types and forms of (im)mobilities, the interconnectedness of mobile and immobile populations, and changes in aspirations and capabilities of life-course decision-making over time.



Immobility becoming a research topic
Emerging trends of (international) mobility resulted in the proclamation of the Age of Migration by the end of the 1990s (see Castles and Miller, 1993) and the identification of a mobilities turn in the context of migration studies at the beginning of the 2000s (see Sheller and Urry, 2006). In recent years, however, the non-mobile population has also received academic attention, with some authors emphasising that the majority of populations are staying put worldwide and that further research is needed to explain the reasons, causes, and consequences of this phenomenon (Schewel, 2020;Mata-Codesal, 2015). Not only have authors started to focus theoretically and conceptually on immobile populations, but increased patterns of immobility have also been discovered as an emergent trend for some types of population and in some parts of the world (Champion et al., 2018;McCollum et al., 2020;Cooke, 2011). Decreasing rates of internal migration have been observed in some countries of the "western world", on the one hand, which can partly be traced back to a stronger rootedness in place and thus constitute voluntary behaviour. On the other hand, the involuntary immobilisation of populations potentially willing to migrate has also become an important field of interest in migration studies. Although evidence for increased immobility can only be found for some population subgroups in some countries, these increasing immobilities have already challenged the contemporary understanding of migration decision-making in migration studies and population geography, due to the difficulties of explaining why people (increasingly) decide not to move (Schewel, 2020;. The mobilities turn in social sciences has recognised not only increasing mobility but also different types of mobilities (King, 2015) and the importance of immobilities and phases of mooring (see Cresswell, 2010). The focus on immobilities offers a new research agenda to explain and better understand the realities of migration and lives across space (Barcus and Halfacree, 2018:1) throughout the course of life. The following paper aims to give an overview of recent scholarship dedicated to the topics of immobility and staying as emerging topics in the context of population geography. While sedentary behaviour has often been considered the norm, not worthy of being put in the front line of investigation, recent studies provide opportunities to E. Gruber: Staying and immobility: new concepts in population geography? A literature review reconsider and reconceptualise thoughts on immobility and staying not as residual to non-mobile behaviour but rather as active choices of individual agency (Erickson et al., 2018;. This literature review is based on literature gathered through (a) a systematic review of a keyword search 1 in the Web of Science database (Booth et al., 2016); (b) snowballing of additional key papers and edited volumes 2 (Wee and Banister, 2016); and (c) a database keyword search in human geography journals in Germany, Austria, and Switzerland. It aims at capturing the discourse in the Germanspeaking community of population geographers. 3 This was of interest, since the author was inquisitive as to whetherand if so, to what extent -the concept of immobilities was already being discussed and used within the German-speaking community. From the first analysis, (a) 371 papers were selected from the Web of Science search, of which 187 were analysed (with 47 of them chosen as "key papers" to be analysed in detail, since they supported the understanding of the conceptualisation of immobilities and/or represented innovative and novel research results). A total of 113 papers were found to be outside the scope of the topic, yet they were used to see how the term immobility has developed from being a concept mainly used in the context of economics to being a common term in migration studies.
The search included journals from the disciplines of anthropology, economics, geography, political sciences, sociology, social sciences, and regional research. The articles were published between January 2000 (the earliest possible year for the database search) and July 2020 (when the database search was performed). In a further analysis, (b) an additional 24 publications were included in the review as key papers and texts for the topics of immobility and staying. A complete list, subdivided by category, is provided in the Supplement. All publications were reviewed for the importance of their content according to empirical insights, methodologies, theories, and conceptual models (Wee and Banister, 2016). This paper will provide an overview of the status quo of literature on immobility research in different fields of social sciences, with particular focus on population geography (Sect. 2). It will then explain types of immobile populations and influ-1 The keywords "immobility", "immobilities" as well as "(im)mobility" and "im/mobility" were used for the keyword search. 2 The snowballing was mainly based on the edited volume of Champion et al. (2018), including research on recent publications of the authors involved.
3 For this keyword search, the same keywords were used as those used in the first search, adding the German equivalent (Immobilität) as well as "mobilities", "internal migration", "staying", and their German equivalents. The following journals were targeted for the search: Die Erde, Erdkunde, Europa Regional, Geographica Helvetica, Geographische Zeitschrift, Informationen zur Raumentwicklung, Mitteilungen der Österreichischen Geographischen Gesellschaft, and Raumforschung und Raumordnung. encing factors for being and becoming immobile, as well as theoretical frameworks and methodologies for immobility research (Sect. 3). This will lead to a discussion of open research questions, necessary methodological innovations, and research gaps detected in recent studies (Sect. 4). The research aim is to determine the degree to which immobility and staying represent meaningful (new) concepts for population geography and hold potential for future scholarship.

Overview and status quo of immobility research
At the beginning of the 2000s, the term immobility was used mainly for labour market immobilities and social immobilities. Texts originating from sociology, economy, or economic geography focussed on socially upward mobilities, especially considering gender, class, and race as distinguishing factors (e.g. Zühlke and Goedicke, 2000;Korupp et al., 2002;Bihagen, 2001;Wanner, 2005). Later, immobility became a term used in the context of migration studies, describing voluntary and involuntary forms of immobility such as staying, waiting, or being stuck, for different types of potentially mobile populations, ranging from labour migrants and refugees to residential migrants. Three major causes eventually led to an increased research interest in immobilities throughout the 2000s: (a) the mobilities turn in social sciences, (b) increasing regulations for international migration and the observation of the immobilisation of populations, and (c) the observed declining internal mobility in western societies (mainly the USA) (Cooke, 2011;Foster, 2017;Champion et al., 2018).
Papers focussing on immobilities in the context of migration studies started to increase in the mid-2000s, especially around the 2010s, very often taking the mobilities paradigm as a starting point. The mobilities turn in migration studies underlined the importance of mobility for contemporary societies and proposed replacing the sedentary logic that had previously been predominant with a mobilities logic, underlining that almost everyone is constantly on the move rather than sedentary (Sheller and Urry, 2006). The mobilities paradigm allowed for consideration of the existing different types of movement. It recognised that migration is extraordinarily complex and that it includes phases of mooring, onward migration, and return migration. It further acknowledged that migration intentions change over time. It is worth mentioning that the new paradigm also incorporated movements other than migration within the framework of mobilities, including commuting, travelling, and all types of circular migration, as well as virtual mobility. In a next step, the exaggerated focus on mobilities seems to have triggered the interest of scholars in sedentary behaviour, as authors identified a mobility bias within migration studies (Ayeb-Karlsson et al., 2020;Glick Schilller and Salazar, 2013). This necessitated the reconceptualisation of immobility and staying as meaningful processes and not as residual to migration (Cooke, 2011(Cooke, , 2013Schewel, 2020).
Although criticised for disregarding the sedentary population, the mobilities paradigm can be seen as an important milestone for immobility research, since it underlined the relation of mobilities and immobilities as well as their underlying aspirations and forces (Sheller, 2014;Glick Schiller and Salazar, 2013;Cresswell, 2012). Mobility and immobility are increasingly seen as lying on a continuum and are therefore often termed "im/mobility" or "(im)mobility" and most commonly used as a plural to subsume different forms and types of (im)mobile (non-)movements, also called the immobilities turn (Bélanger and Silvey, 2020).
Political studies literature focusses on immobilities in the context of increasing restrictions in migration governance, resulting in (involuntary) immobility and immobilisation (Lubkemann, 2008;Bauböck, 2001). Mobility research in anthropology and human geography has underlined the importance of power and social hierarchy and the ways in which both are produced by mobility (Cresswell, 2012;Glick Schiller and Salazar, 2013). This is equally observable in immobility research undertaken in these disciplines, e.g. in studies that highlight the differences between immobile (local) and highly mobile (cosmopolitan) populations (Forsberg, 2019). Recently observed geographies of discontent and backlashes against globalisation (such as Brexit votes) even justify a greater focus on immobile and local populations (Lee et al., 2018;King, 2015). Power inequality and the social hierarchy of immobile versus mobile populations are also topics in the context of the production of place (e.g. through investment, capital flows) and gentrification (Franquesa, 2011). The perspectives of gender norms as well as cultural and social norms and (im)mobilities are further important aspects of immobility studies (e.g. Vaiou, 2012;Conlon, 2011;Mata-Codesal, 2015) since they can explain the selectivity of (im)mobilities. In population geography, many (quantitative) studies conceptualise immobility as the slowing down of the internal migration of different population (sub)groups, mainly in North America, the UK, and Australia. Qualitative studies in population geography have widely focussed on stayers in rural contexts or smaller urban areas (e.g. Erickson et al., 2018;Hjälm, 2014;Barcus and Shugatai, 2018).
Publications written in German or published by Germanspeaking authors of population geography and human geography have only received the discourse on immobilities marginally. Generally, only a few studies have been dedicated to the European immobile population (e.g. in Sweden and Germany) (Bernard and Kolk, 2020;Sander, 2018), with the exception of studies from the UK. Although research on staying decisions especially in rural areas represents a rather traditional field of study, the current debates on immobilities and the "mobilities discourse" seldom appear in German secondary literature (with some exceptions; see Steinführer and Lengerer, 2020;Kordel and Weidinger, 2019;Sander, 2018;Glorius, 2016;Scheiner et al., 2013). Staying or migration decision-making connected to internal migration, however, is a traditional topic in the German-literature discourse. Staying has been discussed (a) in the context of staying on peripheries and in rural areas with a focus on young people, often also from a gender perspective (see Leibert, 2016;Wiest, 2016;Weber, 2016;Oedl-Wieser et al., 2018); (b) in the context of the staying decision-making of international migrants to Germany (students, guest workers, and refugees) and their prospects of staying or returning (see Kordel, 2017;Glorius, 2016;Chilla et al., 2008); and (c) in the context of east-west migration, regional disparities, and regional development (see Leibert, 2020;Nadler, 2012;Glorius, 2010). Immobility is a recognised term in the German-speaking community in the context of migration and climate change. Here it is considered one outcome of livelihood decision-making (see Sakdapolrak et al., 2016;Hillmann and Ziegelmayer, 2016). The topic of immobilities further emerges in the broad discourse on multi-locality. Although multi-locality is widely acknowledged as an indicator for increased mobility, intensified multi-local tendencies have also been associated with a reduced readiness to move (see Ralph, 2015) and thus represent a form of immobility (see Danielzyk et al., 2016).

Theoretical frameworks and methods for immobility research
With the introduction of the mobilities approach, the interconnectedness of mobilities and immobilities and their fluid changes over time, space, and scales became apparent. Studies have pointed out that mobility and immobility cannot be considered opposites but that they are related phenomena and that individuals shift from one status to the other during their lifetime Ortiga and Macabasag, 2021;Coulter, 2013). This complicates the attempt to apply theoretical frameworks that see "the decision to move" as the starting point for studying mobility, not allowing a holistic perspective on mobile and immobile outcomes of lifecourse decision-making. To understand why people do (or do not) move, it therefore became necessary to apply different frameworks that offer an outcome open to either possibility. The aspirations-capabilities model recognises both the structure and the agency that shape people's movement and non-movement as an output based on different aspirations (desires and wishes) and capabilities (personal resources and financial, social, or cultural capital), successfully merging immobility and mobility as two different outputs of the same decision-making process (Schewel, 2020;Carling and Schewel, 2018;Carling, 2002). As staying is "not a decision . . . made once and never renegotiated" (Hjälm, 2014:579), authors have demanded more sensitivity to time and temporalities of migration aspirations and capabilities 278 E. Gruber: Staying and immobility: new concepts in population geography? A literature review (Ortiga and Macabasag, 2021;Mata-Codesal, 2015;Kordel and Weidinger, 2019). Decisions on where and how to live are attributed to certain life events, which may trigger different aspirations over time. This is why the life-course perspective is widely used as a theoretical framework for mobility and immobility research Coulter et al., 2016;Coulter, 2013). Life-course events and transitions (education, careers, partnership, or family formation) are the main "triggers" for (im)mobility decision-making, very often connected to place and housing requirements. The lifecourse perspective recognises individual agency as well as its embeddedness in macro-and meso-structures.
Place attachment serves as an important framework for explaining staying preferences and immobility decisions, especially mentioned in the context of rural areas . The term describes the bonding of people with places, based on affections, cognitions, and practices (Gustafson, 2006) and as such leads to a form of belonging or a sense of community, very often interwoven with social factors and memories but also with perceived amenities and (natural) qualities . Immobility has traditionally been described as a contrast to increasing modernisation and globalisation (Champion and Shuttleworth, 2017), as the withdrawal from global competition, or as staying behind . While trends of immobility present a disruption for some classic migration theories (Lee, 1966), others have expected (internal) migration to decline with the increased advancement of society (Zelinsky, 1971;. Changes in observed (im)mobility patterns therefore challenge "how the nexus between migration and development is theorised" (McCollum et al., 2020:3) and question the degree to which increasing immobilities are connected to social inequality (McCollum et al., 2020:3) In recent studies, scholars have applied qualitative and quantitative methods in immobility research. Population geographers have engaged in observing new trends in internal migration (see Champion et al., 2018). The increased engagement with internal immobility can be related to improved datasets and novel, innovative approaches involving longitudinal and combined data, which have become possible due to new forms of data collection (see e.g. McCollum et al., 2020;Bell et al., 2018). In order to explain gender, race, or ethnic variations; the importance of linked lives; and temporal dynamics in relation to different places, researchers have increasingly begun to draw on new possibilities by deploying material from survey and register data, considering that these types of data are rich in information (Barcus and Brunn, 2009;Coulter et al., 2016). Unfortunately, even in those few countries where these kinds of data are collected, access to them is often rather limited. Researchers have called for better cooperation with statistical offices as a potential way forward in favour of new approaches in quantitative analysis and for better availability of existing data (McCollum et al., 2020;Bernard and Kolk, 2020). Until now, qualitative analy-sis has primarily served to explain immobilities better. Qualitative research results constitute the main empirical element of design and differentiation between voluntary and involuntary forms of immobility. Yet, researchers continue to call for further application of theoretical frameworks and for further qualitative research in order to gain better insight into immobility decision-making (Schewel and Fransen, 2020).

Types of immobility and staying
Conceptions of "immobile populations" vary greatly throughout the literature and can mainly be distinguished by "their degree of (in)voluntariness" (Mata-Codesal, 2015:2279. Especially in the context of international migration, the immobile population is often perceived as those people unable to leave due to a lack of resources or a lack of the capital needed to achieve a relocation, those people who are stuck, or those people who are waiting for the opportunity to migrate (e.g. Gross-Wyrtzen, 2020; Blondin, 2020; Conrad Suso, 2020). There are however various types of immobile and sedentary population, including voluntary stayers (Mata-Codesal, 2018). "The diverse terms describing immobility or immobile people includes everything from involuntary immobility, stayers, non-migrants, staying put, and left behind" (Ayeb-Karlsson et al., 2020:2). Mata-Codesal identifies three types of stayers: desired, acquiescent, and involuntary. She supports this classification by a case study conducted in Ecuador, where a significant proportion of the population follows mobility pathways internally or internationally for the sake of education or employment (Mata-Codesal, 2015). Involuntary immobility is based on the definition of Carling, who uses the term to describe a person willing to move internationally but who is unable to do so (Carling, 2002;Mata-Codesal, 2015). Schewel, who bases the idea on the capabilities and aspirations framework (see Sect. 4.2.2), originally introduced the concept of acquiescent immobility. An acquiescent stayer has no capabilities to migrate but also no aspiration to do so (any more) and therefore, in contrast with an involuntarily immobile person, accepts his or her own inability to realise plans of emigration (Schewel, 2020). Ortiga and Macabasag (2021) draw on the example of aspiring nurses in the Philippines who had planned to migrate but eventually ended up staying and letting go of their migration aspirations due to too many obstacles arising (2020). In their study Ortiga and Macabasag (2021) not only empirically draw on the type of acquiescent stayers but also underline the importance of temporalities in (im)mobility decisions and decision-making (see Sect. 4.2.4). Desired immobilities are "[o]n the opposite side of the voluntary-forced immobility spectrum" (Mata-Codesal, 2015:2281), describing someone who "stays put as the consequence of a conscious decision" (Mata-Codesal, 2015:2281). "Desired immobility is more likely to be present in contexts where staying put is associated with processes of upward social mobility" (Mata-Codesal, 2015:2282). For voluntarily immo-bile persons, staying put is often connected to (social or economic) advantages of staying, often bound to a specific location and potentially lost when leaving (Mata-Codesal, 2015:2282Hjälm, 2014). The three types cannot be separated clearly, and they also change over time. Drawing on the decision-making process of an indigenous population in the Pacific, Farbotko and McMichael (2019) demonstrate that only a few decision-making processes can be defined as entirely voluntary or involuntary. Barcus and Brunn (2009) have created a typology of place attachment and mobility that includes mobility restriction and places the focus on internal mobilities. The immobility type "rooted in place" consists of individuals who remain in place by choice over their lifetime, having a strong attachment to place and very little interest in moving away from their home county. For those who choose to remain, networks of family and friends and involvement in local organisations, as well as social groups, are important for their continued residence. The immobility type that is "tied to place" has a weaker place attachment and has moved often but mostly within the home country. These persons generally have a lower income, and very often their decisions to move are not entirely voluntary but result from personal economic, social, or health crises (family dissolution, inability to pay rent, caring obligations, housing insecurity). The type "mobile with strong place attachments" displays a strong attachment to place but becomes mobile due to employment or education opportunities. The typology shows that staying can be connected to privilege and that the ability to leave for improvement is equally built on resources. While a few respondents choose long-term immobility, it is imposed (economically or socially) on others. Clark et al. (2017) mention the different levels of staying, drawing on residential mobility research in Granada, Spain, and the importance of the concept of scale (home, neighbourhood, local, national) when conceptualising staying. For Cuervo and Cook (2019), return migration also signifies a type of staying, building on belonging and nostalgia as frameworks.
Waiting or being stuck are depicted as special types of immobility, very often connected to linked lives and a gendered perspective on immobility (Straughan et al., 2020;Conlon, 2011;Allerton, 2020). The term trapped population has been widely used to refer to populations living in areas at risk due to environmental changes and climate change. The term is criticised, however, since people are not always trapped but often choose to stay, even in places with suboptimal conditions, due a variety of other factors (Adams, 2016;Farbotko and McMichael, 2019;Ayeb-Karlsson et al., 2020). Authors advocate using the term trapped population carefully and recognising people's preference for staying, even in environmentally high-risk areas (Farbotko and McMichael, 2019). There is also some discomfort with the term left behind, implying passivity in the processes of choice regarding the immobility of linked family members (Mata-Codesal, 2015:2285 and creating a hierarchy between the mobile and the local, although stayers very often represent an important bridge and connection for the mobile population (Barcus and Shugatai, 2018).

Reasons for and factors influencing (increasing) immobility and implications of immobilities
International and involuntary immobility has been strongly associated with increasing barriers to migration as well as with increasing migration governance. Internal nonmigration trends are generally associated with emotional and social bonds, social networks, family and kin, engagement with place and organisations, quality of life, and the feeling of belonging (Barcus and Brunn, 2009;Hjälm, 2014, Milbourne andKitchen, 2014). In quantitative studies, the slowing down of mobility has partly been explained with demographic ageing or more (secular) rootedness (Cooke, 2013;Kalemba et al., 2020). In recent years, it was however discovered to be heavily dependent on economic factors, e.g. on fewer economic returns when switching jobs and/or on geographical locations (Haan and Cardoso, 2020). It is also identified as an active response to managing precarious labour market conditions and employment (Preec, 2018). Cooke (2011) finds 63 % of the migration decline in the USA is connected to the economic crisis starting in 2007 (Cooke, 2013). In Spain, the economic crisis has likewise led to a major decline in spatial mobility (Palomares-Linares and van Ham, 2020). Only 17 % of the decline in internal migration in the USA is attributed to demographic change (Cooke, 2011) and 20 % to an increased "secular rootedness" of American citizens (Cooke, 2011;Fischer, 2002). Kalemba et al. (2020) support a shift in (internal) migration behaviour in Australia beside a strong impact of population ageing (Kalemba et al., 2020). Changing migration behaviour is influenced by the rise in ICT, with the consequence that a job change no longer automatically has to lead to a change in residence (Cooke, 2013;Kesselring, 2006). This allows residential rootedness and migration to be substituted with other forms of (virtual) mobility , such as seasonal mobility, (long-distance) commuting, or multi-local living patterns (Povrzanović Frykman et al., 2020). It represents "alternative time-space strategies", allowing distant socio-economic opportunities while remaining local (Milbourne and Kitchen, 2014). Further, the increase in dual-worker couples ("power couples"; see Kalemba et al., 2020), changing gender roles, increasing rates of homeownership, and rising housing prices are seen as main factors in mobility decline in the USA, Australia, and the UK (Kalemba et al., 2020;Cooke, 2013;Mc-Collum et al., 2020).
From qualitative studies, we learn that reasons for immobility and staying are generally complex and multifaceted (Hjälm, 2014;Mata-Codesal, 2015;. The general tenor in immobility research is that immobility is unquestionably an active process (Erickson et al., 2018;Preece, 2018;Hjälm, 2014). Besides, the general absence of reasons for leaving or of alternative attractive places to go is also a trigger for staying decision-making (Hjälm, 2014). Staying and immobility (also in the context of return) can be triggered by nostalgia (Cuervo and Cook, 2019). Staying and leaving decisions are often not taken by individuals alone but rather are complex family strategies Mulder, 2018;Hjälm, 2014). Focussing on areas with reduced economic perspectives and low rates of moving (see Preece, 2018) can provide interesting insights into the reasons why people decide to remain immobile, despite objectively better opportunities offered in other places.
The mobility of a population is assumed to have a positive outcome for economies, since higher degrees of mobility mean faster adjustment to economic shocks (Caldera Sánchez and Andrews, 2011), as internal migration, for example, "is one of the prime mechanisms by which labour demand and supply are matched at local and regional spatial scales" (Stillwell et al., 2018:59). Immobility is therefore connected to negative implications for economic development and competitiveness (Caldera Sánchez and Andrews, 2011). Greater rootedness is usually paired with community cohesion, greater social stability, and lower crime rates (Champion and Shuttleworth, 2017;Fischer, 2002) as well as with community satisfaction (Erickson et al., 2018). "Location-specific insider advantages"  might allow the immobile population to profit from economic advantages (Schewel, 2020). If migration decline is related to increasing inflexibilities in labour and housing markets, it may become a policy concern but might also signal improved job matching and possibilities in local labour markets (Kalemba et al., 2020). Research on changes in (im)mobility patterns is therefore of concern for policy-makers and society, as it plays a key role in national and subjective wellbeing (Green, 2018).

Discussion -open questions for future research
Extant literature reveals that there is an increased interest in immobilities and the underlying decision-making processes. Most recent studies understand mobility and immobility decision-making as a continuum and underline that both mobility and immobility can be possible outcomes of life-course decision-making (Schewel, 2020;Erickson et al., 2018;Cooke, 2011). Today, various new forms of mobility (digital, short-term, fluid, or circulating mobilities) also provide alternatives to migration and open up new possibilities in terms of immobility (e.g. when taking up a job, leading transnational or trans-local lives, or when commencing further education). Thus, the very idea of mobility or immobility becomes blurred. With the concept of immobility, certain phenomena that have hitherto been discussed as outcomes of a hypermobile society, such as multi-locality or long-distance commuting, might be seen in a new light and eventually be understood as immobility practice (see also Wood et al., 2015).
Studies underline that outcomes of (im)mobility decisionmaking are interwoven and dependent on temporalities, e.g. from a perspective of linked lives or concerning the idea of changing aspirations over time (Ortiga and Macabasag, 2021;Carling and Schewel, 2018;Coulter et al., 2016;Coulter, 2013;Mata-Codesal, 2015). This is also generally true concerning the potential of various outcomes of life-course decision-making. This consideration has inspired authors to use new and innovative datasets, as well as to apply and design novel theoretical frameworks for immobility research. In order to obtain a better insight into sequences of (im)mobilities over the life course, authors agree that there is a demand for further longitudinal studies to understand how aspirations change over time (McCollum et al., 2020;Bernard and Kolk, 2020). In many studies, (internal) migration datasets serve as the main information for immobility (see Champion et al., 2018). Further methodological elaborations that take sedentariness into account (e.g. measuring the length of stay, residence time, fluidity of population) are rare and might allow new results. Of course, data for such analyses are relatively scarce, but with register data becoming available in more countries in the future, the sedentary population as well as the interplay of mobility and immobility could become more central, as opposed to the mere observation of the slowing down of the mobile population. Qualitative studies can also make greater future use of panel analysis and longitudinal research designs and, in doing so, incorporate the time dimension. Surveys designed to focus on the various types of mobile and/or immobile populations would be able to provide empirical evidence for theoretical considerations.
Thematic emphases are distributed unevenly in different localities, very often being connected to either voluntary or involuntary immobility and reflecting different motivations in different regions and societies. Involuntary immobility has mostly been associated with international migration (Blondin, 2020;Conrad Suso, 2020;Mata-Codesal, 2018), while voluntary immobility and rootedness in place is rather used in the context of internal migration and especially in the context of qualitative studies focussing mainly on rural areas and smaller urban areas (Forsberg, 2019;Hjälm, 2014;Barcus and Brunn, 2009). For future research, a greater variety of research emphases and applications of the immobility concept might be needed in order to verify its necessity. Using it for research on the challenges of (voluntary or desired) immobility in urban areas could provide a new perspective for gentrification research (as done by Franquesa, 2011). Immobility in the context of housing markets (especially in urban areas) offers potential for future research, not only for desired mobility but also when focussing on restrictions on desired immobilities. While population geographers have internationally taken up the topic of immobilities, such studies are still rare in the German-speaking community. Studies on contemporary patterns of internal migration within the EU and within European countries (including Germany, Austria, and Switzerland) and on their socio-economic implications are rather scarce, compared to the USA and the UK, and would need further attention. Furthermore, transatlantic research comparing implications and reasons for different (and changed) aspirations of (im)mobilities might be of interest.
Scholars' attention to immobilities and their recognition of immobility and staying as processes of active agency gave rise to new empirical, theoretical, and analytical research outcomes in population geography and migration studies. This includes typologies of stayers (Mata-Codesal, 2015;Barcus and Brunn, 2009), as well as studies incorporating mobile and immobile populations (Kordel, 2017;Leibert, 2016;Conlon, 2011). Typologies are mostly related to the degree of voluntariness of immobility decision-making. Immobility is generally strongly connected to place(s) and as such is a topic of interest for population geographers. Research on immobilities underlines the ways in which place is constructed and hierarchised when populations are stigmatised as left behind, trapped, or stuck. It furthermore reveals that remaining in a locality can be connected to resources and privileges (Preece, 2018;Mata-Codesal, 2015). We will need further studies to understand decisions regarding (im)mobilities in their relation to access to resources and privileges and their connection with place, especially for different population subgroups. While place has been considered relevant for immobility decision-making, until now studies have insufficiently considered immobile populations and their importance for places and communities (with exceptions, e.g. Barcus and Shugatai, 2018). Therefore, the scientific community should further pursue the issue of the connection of (im)mobilities, regional development, and community cohesion in order to improve its understanding of the implications of a (more or less) rooted society. Finally, this literature review has been compiled in the midst of the COVID-19 pandemic, at the beginning of an era of immobility, which raises many new research questions on future aspirations and obstacles regarding (im)mobilities.

Conclusion
This paper aimed to provide an overview of the status quo of literature on the topic of immobility and staying as concepts that have recently gained importance in population geography. Immobilities are increasingly being discussed within migration research, underlining that even after the mobilities turn, immobile populations as well as immobile sequences do exist and that decisions for being and becoming immobile often follow decision-making processes similar to those taken in the context of migration and mobility. The paper has discussed different typologies and theoretical frameworks as well as methodologies applied in immobility research. Although many studies have been compiled lately, there are still undisclosed facts and open questions related both to research results and to underlying methodologies. We may conclude that the concept of immobilities offers a meaningful framework for future research in population and human geography, since contemporary research themes, e.g. research on multilocality or gentrification, can profit from this perspective. Focussing on the sedentary population underlines the importance of places for life-course decision-making and furthermore illustrates the ways in which places are constructed by relations and resources, which again relates to potential (im)mobility decisions. Research on immobilities makes sense only when being thought of together with mobilities, not as being opposite to each other but included in a continuum, consisting of various types of (im)mobilities ranging from virtual and circular to actual (non-)movement. Finally, immobility and staying are central concepts in population geography as different types of mobilities are becoming more fluid. Therefore, including different considerations of mobilities and immobilities in one research framework will be necessary for understanding individual decision-making that "emplaces" lives across space. Data availability. The author confirms that the data supporting the findings of this study are available within the article and its Supplement.
Competing interests. The author declares that there is no conflict of interest.