Journal of Public and Nonprofit

This review studies previous research on the role of nonprofit organizations in the co-production of welfare services. The need for the review stems from the lack of systematic literature reviews related to nonprofit organizations, co-production, and welfare services. The empirical material is delimited to peer-reviewed research published in international academic journals and analyzed in relation to levels of co-production, the role of organizations, and nonprofit organizational distinctiveness. Main findings include that research has primarily studied the role of nonprofit organizations in relation to co-production and enabling favorable conditions, and that existing research identifies several potential distinctive contributions made by nonprofit organizations to co-production. Implications include encouraging co-management of welfare services, enabling co-production in welfare services beyond public organizations, and exploring how different types of organizations contribute to co-production.


Introduction
What do we know about the role of nonprofit organizations in the co-production of welfare services?Many countries are searching for new ways to provide and govern welfare in order to meet major demographical, political, and economic challenges (Pestoff, 2009).Coproduction is promoted as one of these ways, as it is said to provide a model for the mix of professionals and users as well as different organizations and sectors to contribute to the provision of welfare services (Brandsen & Pestoff, 2006;Brandsen et al., 2018;Ibsen, 2021;Ostrom, 1996;Parks et al., 1981;Verschuere et al., 2012).Even though co-production is far from a panacea (Brandsen & Helderman, 2012;Porter, 2012), research has established that co-production could increase quality, democratic participation, and user satisfaction, among other results (Rantamäki, 2017;Segnestam Larsson et al., 2021;Vamstad, 2012).
Many examples and illustrations of the role and significance of nonprofit organizations in the co-production of welfare services can also be identified in research (Brandsen & Pestoff, 2006;Neubeck, 2016;Pestoff et al., 2006).For example, nonprofit organizations are said to facilitate, enhance, and promote user participation to a higher degree, while their role at the same time mainly is limited to producing services together with users rather than managing or governing the organizations that deliver these services together with users (Pestoff, 2009;Prentice, 2006;Vamstad, 2012).There also exists research on how nonprofit theories and frameworks can inform research on co-production (Benjamin & Brudney, 2018).
Despite a significant amount of research coupled with numerous empirical examples (Brandsen & Pestoff, 2006;Pestoff, 2012;Verschuere et al., 2012), there appears to exist relatively little comprehensive knowledge related to the role of nonprofit organizations in the co-production of welfare services.In comparison, among the many existing systematic reviews of co-production (Clifton et al., 2020;Jukić et al., 2019;Rodriguez Müller et al., 2021;Voorberg et al., 2015), there is no review that solely focuses on the role of nonprofit organizations in relation to co-production.
The aim of this article is to contribute to previous research by presenting the results of a systematic literature review of the role of nonprofit organizations in the co-production of welfare services.The research questions that direct the article are: • What is the role of nonprofit organizations in the co-production of welfare?
• To what degree do users and professionals produce, manage, and govern welfare services together in nonprofit organizations?• In what ways do nonprofit organizations make unique contributions to co-production?
It should be noted that there exist many different definitions and understandings of coproduction (Brandsen & Pestoff, 2006;Loeffler, 2021a;Pestoff, 2012) and similar concepts in the literature, such as co-creation (Brandsen et al., 2018;Loeffler, 2021b;Rodriguez Müller et al., 2021;Torfing et al., 2019;Voorberg et al., 2015), although some argue that for example coproduction and co-creation are conceptually distinct (Torfing et al., 2019).Co-production is in this article defined as a process that takes place between users and professionals, rather than as processes in the collaboration between, for example, the public and the nonprofit sector, between public and nonprofit organizations, or between public organizations and external stakeholders (Brandsen et al., 2018;Ibsen, 2021;Jukić et al., 2019;Verschuere et al., 2012).
The next section presents a framework for analysis, related to the role of nonprofit organizations in the co-production of welfare services.The framework is used to code and analyze the empirical material.The methodology and the empirical material are then described, followed by a presentation of the findings in relation to publication characteristics and the role of nonprofit organizations in co-production.The results of the review are in the analysis and the discussion related to more general literature reviews on the role of coproduction in welfare (Verschuere et al., 2012) and literature reviews on co-production in public organizations (Rodriguez Müller et al., 2021;Voorberg et al., 2015).The article is concluded by listing the main contributions to the knowledge base as well as by pointing out implications for policy, practice, and research.

Framework for Analysis
Commonly used conceptual frameworks for identifying and discussing the role of nonprofit organizations in societal affairs-such as nonprofits as avant-garde, complement, alternative, or replacement (Lundström, 1996)-fit less well with the definition of co-production used in this article.One main reason is that these frameworks seek to categorize the role of nonprofit organizations primarily in relation to a dominant actor, such as the government and its public organization.The goal in this article is less to understand the role of nonprofit organizations in relation to the state, and more to tease out the specifics of the role of nonprofit organizations in relation to the type of co-production that takes place between professionals and users (Brandsen et al., 2018;Ibsen, 2021;Jukić et al., 2019;Verschuere et al., 2012).
In this article, levels of involvement and the role of nonprofit organizations in co-production will be used for understanding, coding, and analyzing the relationship between nonprofit organizations and co-production of welfare services.Levels refer here to the focus of the involvement of users and nonprofit organizations, such as an individual or an organizational level.The role of nonprofit organizations highlights the different roles these organization can have in co-production, such as enabling or delivering services.In addition to levels and roles, I will also identify and analyze if, and if so, to what degree nonprofit organizations make distinctive contributions to co-production of welfare services.These three dimensions of coproduction, constituting the framework for analysis, are introduced below.

Levels of Involvement
Research has long since noted that co-production could focus on different levels (micro-mesomacro), and furthermore that users and nonprofit organizations could engage at different levels (individual-organizational-societal) (Brandsen et al., 2018;Loeffler, 2021a;Pestoff, 2012;Voorberg et al., 2015).Based on typology related to nonprofit and state relationships (Osborne & McLaughlin, 2004), Brandsen and Pestoff (2006) have developed a conceptual framework related to the original concept of co-production.The framework was developed partly because of the observation that the term co-production has been used in different contexts and for different phenomena (Brandsen & Pestoff, 2006;Loeffler, 2021a;Pestoff, 2012).The conceptual framework distinguishes the following three manifestations of coproduction, here referred to as 'levels of involvement': • Co-production refers to a level of involvement in which users and nonprofit organizations partly or fully participate in the production of services.• Co-management concerns involvements in which users and nonprofit organizations participate in the management of services.• Co-governance refers to a level of involvement in which users and nonprofit organizations participate in the formulation of policies and planning of services.
In an article published six years later, Pestoff (2012) clarifies that both co-production and comanagement take place on the output or implementation side whereas co-governance usually could be found on the input side.It should furthermore be noted that the levels of involvement are not mutually exclusive.Nonprofit organizations could for example have structures that enable participation of users, combining co-production and co-management.Like Brandsen and Pestoff (2006), I refer to all three levels of involvement under the heading of coproduction.Other researchers have also used the concepts of co-governance and comanagement in a similar fashion (Lindsay et al., 2018;Poocharoen & Ting, 2015).

Role of Nonprofit Organizations
Whereas levels of involvement refer to if co-production focuses for example on production or management, the role of nonprofit organizations highlights the extent to which nonprofit organizations are involved in co-production.Based on a review of research on co-production in general (Verschuere et al., 2012), a framework is therefore developed and presented in this article that distinguishes between enabling, providing mechanisms for, and delivering coproduction.
• Enabling favorable conditions for co-production.These conditions could include supporting, connecting, and protecting users, proving legitimacy for co-production as a norm and praxis in society, or other circumstances that may hinder or facilitate coproduction.• Providing organizational mechanisms for co-production.Mechanisms may include organizational structures that enable participation, promote innovations in the production or management of welfare services, or uphold key variables that are required for co-production to take place.• Delivering results.This degree of co-production refers to nonprofit organizations being directly involved in the production and provision of welfare services, such as childcare or home support.
Like levels of involvement, the three themes are only to be considered as analytical devices and may therefore not be mutually exclusive in real world examples.For example, participation could be regarded as a mechanism for co-production (as co-production could be defined as users participating in the production of welfare services; see, for example, Brandsen et al., 2018;Verschuere et al., 2012) as well as the key outcome of co-production (as research has established that co-production could increase democratic participation; see, for example, Rantamäki, 2017;Vamstad, 2012).

Distinctive Contributions
Finally, as noted above, the literature also provides many examples of the significance of nonprofit organizations in co-production (Brandsen & Pestoff, 2006;Neubeck, 2016;Pestoff et al., 2006), begging the question if and, if so, to what degree nonprofit organizations make unique contributions to co-production.At times, the concept of distinctiveness has been used to identify unique and essential characteristics and qualities of nonprofit organizations to distinguish them from other societal phenomena (Anheier, 2005;Hall, 1992;Salamon et al., 2000;Smith & Lipsky, 1993).For example, by comparing nonprofit organizations to public and for-profit organizations, researchers discuss how nonprofit organizations at times deliver better quality, and are more flexible and innovative (Kendall, 2003;Roseneil & Williams, 2004;Salamon et al., 2000;Sherman, 2003).Inspired by previous research, distinctiveness is in this article therefore defined as the unique ways in which nonprofit organizations and their activities contribute to co-production in comparison to public and for-profit organizations.For example, in the case of organizations, distinctive contributions could concern the role of organizational missions, ideologies, and values in co-production, or unique forms of access to certain target groups or resources (such as volunteering), and how these characteristics differ from public and for-profit organizations involved in co-production.

Method and Empirical Material
In terms of methodology, a systematic literature review of previous research was carried out in December 2020 (Gough et al., 2012).In terms of methodological steps, a search string was developed based on combining terms related to co-production, nonprofit organizations, and welfare.The search string was then adapted, as their thesauruses were different, and applied to three databases for academic research (Academic Search premier, SocIndex, and Sociological abstracts). 1   The selection of articles was based on pre-defined eligibility criteria (see Figure 1 below).
Report eligibility criteria focused on formal elements and included that the articles should be a) peer-reviewed research, b) written in English, and c) published in international academic journals.The initial search (205 articles) was as a result firstly reduced by deleting duplicates (21 articles), texts that were conference papers (8), and articles written in other languages than English (7).The remaining 169 articles were downloaded.Study eligibility criterion focused on the topics.As this review focuses on co-production, nonprofit organizations, and welfare, I excluded articles that did not address all three topics.Following the study eligibility criterion, I screened the title and abstracts of the 169 articles, out of which I deemed 110 articles to be less relevant for the review.

Figure 1. Selection Process
The resulting 59 articles, covering a period between 1999 and 2020, were coded by the author with the support of software for qualitative analysis (Nvivo).The purpose of the coding was to organize the articles and their various dimensions as well as to analyze these dimensions.The articles were coded firstly in relation to ( 1) publication year, (2) the origin of the article, (3) the main nonprofit concept, (4) type of research approach (theoretical/empirical), and (5) methodological orientation.
Thereafter, the articles were coded in relation to the framework for analysis, that is (6) levels of involvement in co-production (Brandsen & Pestoff, 2006), ( 7) the role of nonprofit organizations (Verschuere et al., 2012), and (8) the degree to which nonprofit organizations are said to make distinctive contributions to co-production (Anheier, 2005;Hall, 1992;Salamon et al., 2000;Smith & Lipsky, 1993).The results of the analysis are presented in the next sections.Excluded on: Studies included in review (n = 59)

Origin and Nonprofit Concept
Most articles relate to a European context.36 of the articles are from or based on material from European countries or the European region.In more detail, 15 articles could be attributed to the United Kingdom.If articles from England and Scotland are attributed to the United Kingdom, the total amount rises to 22 articles, making the United Kingdom an exception in this research field.This is noteworthy as it has been argued that the field of coproduction originally had been developed in the context of the so-called 'residual' welfare states (Esping-Andersen, 1990), such as Great Britain, the US, Holland, and Belgium (Bovaird, 2007;Parks et al., 1981;Pestoff, 2012).The next largest region in terms of number of articles is North America, including six articles from or based on material from the United States and six from Canada.Four articles could be related to Australia and Denmark, and two from Germany and Italy.The remaining articles originate from different countries, such as the Netherlands, Sweden, and China.
The main concepts for denoting matters related to the nonprofit sector were the third sector (14 articles or 24%) and community (11 articles or 18%).The prominence of the concept of the third sector could partly be attributed to the finding that most articles relate to a European context, as some European scholars and research traditions have favored the concept of the third sector over other concepts.Furthermore, ten articles (17%) used primarily the concept of volunteers, five articles (9%) used non-government, and three (5%) used civil society.Only two articles (3%) used primarily the concept of nonprofit.I was not able to identify a concept related to the nonprofit sector for seven (12%) of the articles.

Type of Research Approach
Of the 59 articles studied, I deemed 47 (80%) to be primarily empirically oriented, six (10%) to be primarily theoretically oriented, four to be both empirically and theoretically oriented (7%), and two (3%) un-categorizable.The domination of the empirical orientation of research on nonprofit in co-production seems to be similar to research on co-production in general (Verschuere et al., 2012).
Articles were seen as empirically oriented if they were based on new empirical findings which were essential for the presentations.The empirically oriented articles often addressed coproduction in social work (38%) and health care (34%), including providing services for older people (Doheny & Milbourne, 2013), community participation in rural health services design (Farmer & Nimegeer, 2014), and co-production of community mental health services (Vaeggemose et al., 2018).To a lesser extent, the empirically oriented articles addressed coproduction in education (10%) and other fields of interest (18%), the latter including areas such as research, citizen participation, or membership in associations.
Articles that were not based on primary empirical data, but that rather had the aim of bringing new understanding to the conceptualization of co-production through argumentation (built on existing theories or analytical concepts) were regarded as theoretically oriented.Journal articles with a theoretical orientation included, for example, the application of empowermentoriented approaches to co-production (Breton, 1999), an article that identified four alternate models of user value cocreation (Nambisan & Nambisan, 2009), and an article that discussed hybridity in relation to nonprofit organizations and co-production (Pestoff, 2014).
Four articles were deemed to be both empirically and theoretically oriented.One example of such an article is the article, An Ambiguous Concept: On the Meanings of Co-production for Health Care Users and User Organizations? (Ewert & Evers, 2014).Presenting empirical material from the health care sector in Germany, the article also addresses the vagueness of the concept of co-production, arguing for example that uncertainty and ambiguity is the normalcy when it comes to define co-production.
Finally, there were different reasons for not categorizing the remaining two articles into any of the groups.One article had neither an empirical nor a theoretical orientation (Brown et al., 2005), the other promoted an online toolkit for co-production for community based participatory research (Goodman et al., 2018).

Methodological Orientation
Similar to reviews of research on co-production in general (Verschuere et al., 2012), a significant portion (20%) of the research on nonprofit organizations, co-production, and welfare services is case study based (Morton & Paice, 2016;Tarlau, 2013;Vaeggemose et al., 2018).Furthermore, and partly as a result of case study designs, but also the prevalent use of interviews and participatory and action research methods, most authors use qualitative data (59%) (Baker & Irving, 2016;Jagosh et al., 2015;Lum et al., 2016).There are a smaller number of articles using quantitative methods (10%), including surveys and mappings (Lelieveldt et al., 2009;Thomas et al., 2011;Vamstad, 2012).There are also a set of articles using a mix of methods (10%), including a combination of quantitative and qualitative methods (Ewert & Evers, 2014;Sadler et al., 2017;Strokosch & Osborne, 2017).Finally, it was difficult to categorize the methodology for some articles (21%) due to factors such as theoretical orientation or the use of secondary material (Farmer et al., 2015;Goodman et al., 2018;Young et al., 2017).The aforementioned review of research comments on the qualitative nature of coproduction research, arguing that it, on the one hand limits the scope of findings, but that these limitations also are understandable given the continued conceptual discussions surrounding co-production (Loeffler, 2021a;Pestoff, 2012;Verschuere et al., 2012).

Results
In addition to findings related to publication characteristics, articles were also categorized in relation to levels of involvement, the role of nonprofit organizations as well as if they addressed potential distinctive contributions made by nonprofit organizations to co-production.

Levels of Involvement
As presented in the framework for analysis, levels of involvement refer to if co-production focuses on production, management, or governance (Brandsen & Pestoff, 2006).In the selection of 59 articles, I categorized 35 (59%) as mainly focusing on co-production, four (7%) to be primarily focused on co-management, 18 (30%) as focusing on co-governance, and two (3%) to be un-categorizable (Kuts, 2002).Even though the applied framework only differentiates between three levels of involvement, it should be noted that the selected articles used a variation of concepts related to co-production, including co-design (Farmer et al., 2018), co-creation (Brown et al., 2005), and co-construction (Lum et al., 2016).The categorization, however, not only considered the preferred used of concepts, but also the focus of the articles, and finally collapsed the various manifestation into the three included in the framework.
Articles were seen as focusing on co-production if they addressed levels of involvement in which users partly or fully participate in the production of their own service.As expected, given that close to six out of ten articles were categorized as co-production, they displayed a wide range of plurality in regard to origin (Bano, 2019;Breton, 1999;Roberts et al., 2014), the concept used to denote nonprofit (Derges et al., 2014;Ewert & Evers, 2014;Lelieveldt et al., 2009), type of research approach (Alm Andreassen, 2018;Boccacin, 2017;Vaeggemose et al., 2018), welfare area of interest (Doheny & Milbourne, 2013;Evans, 2012;Rantamäki, 2017), and methodological orientation (Lee & Han, 2016;Paterson et al., 2007;Thomas et al., 2011).
Articles that focused less on users producing their own services, and more on the involvements in which users and nonprofit organizations participate in the management of services, were regarded as primarily co-management oriented.The four journal articles with such an orientation included articles that studied the role of nonprofit organizations in the comanagement of promoting asylum seeker integration in Scotland (Strokosch & Osborne, 2017), the facilitation of personal development for public involvement in health-care education and research (Read et al., 2020), and the involvement of parents in cooperative child care in Sweden and Germany (Pestoff, 2012;Vamstad, 2012).
Finally, articles were seen as focusing on co-governance if they addressed levels of involvement in which users and nonprofit organizations participate in the formulation of policies and planning of services.Examples of co-governance-oriented articles tended to focus more on how users and nonprofit organizations participated in the planning and implementation of services at a sectoral level than on the formulation of policies (Bode, 2006;Fazzi, 2009;Jagosh et al., 2015).For example, one article studied involvement of the nonprofit sector and users in the governance of health service provision in the United Kingdom (Martin, 2011), and another article described a pendulum movement over time between co-production and co-governance in the home care services in Canada (Jetté & Vaillancourt, 2011).
Similar to how Brandsen and Pestoff (2006) noted that the categories in their conceptual framework were not mutually exclusive, several examples could be found in which the levels of involvement overlapped in the articles.One such example is the article, Co-production and Service Quality: The Case of Cooperative Childcare in Sweden (Vamstad, 2012).In addition to the use of co-production in the title and the categorization of the article as primarily comanagement oriented, the empirical material presented in the article shows how parents were simultaneously involved in the management of the cooperatives as well as in the production child care.Hence, the levels of involvement are neither to be regarded as mutually exclusive from an analytical perspective nor from an empirical one.

Role of Nonprofit Organizations
In contrast to levels of involvement, I was not able to categorize the role of nonprofit organizations (Verschuere et al., 2012) for more than half of the articles (58%).The main recurring reason for this was that the specific role of nonprofit organizations was simply not addressed.For example, the article, A Coproduction Community Based Approach to Reducing Smoking Prevalence in a Local Community Setting, describes how local residents were recruited and trained as community researchers to deliver a smoking prevalence survey in the United Kingdom (McGeechan et al., 2016).The article does not, however, address the role of nonprofit organizations.
Of the remaining 25 items studied, I categorized ten of the 25 articles (38%) as enabling favorable conditions for co-production, six (23%) as delivering results, and five (19%) as providing organizational mechanisms.I also deemed that one article (4%) paid equal attention to enabling favorable conditions and providing organizational mechanisms (Lelieveldt et al., 2009), and that three other articles (12%) paid equal attention to all three degrees of involvement (Boccacin, 2017;Ewert & Evers, 2014;Pestoff, 2014).
Articles were categorized as enabling favorable conditions for co-production if the role of nonprofit organizations mainly related to circumstances that facilitated co-production.One example of enabling conditions is an article that showed that the highest levels of change related to co-production occurred in the presence of involvement and support of nonprofit organizations (Derges et al., 2014).Other examples of enabling favorable conditions included nonprofit organizations having access to public servants and elected officials (Lum et al., 2016), building relationships and protecting users (Strokosch & Osborne, 2017), enhancing, facilitating, and promoting greater citizen and community participation (Fazzi, 2009;Pestoff, 2012;Thomas et al., 2011).
Articles that highlighted how nonprofit organizations uphold variables required for coproduction to take place were regarded as primarily providing organizational mechanisms for co-production.The five articles placed in this category included examples of providing organizational mechanisms such as co-operatives for users (Prentice, 2006), organizations developing collaborative relationships for patients (Baker & Irving, 2016), nonprofit organizations enabling citizens to be involved as volunteers (Lee & Han, 2016;Vaeggemose et al., 2018), and organizations ensuring good governance to co-production partnerships (Bano, 2019).
Finally, articles that mainly described and analyzed the production and provision of welfare services by nonprofit organizations were seen as delivering results.The six articles categorized as delivering results included studies that analyzed the quality of services in childcare in Sweden (Vamstad, 2012), how member structures and membership in nonprofit organizations affect the creation and delivery of value (Hager, 2014), and the role of nonprofit organization for the supply and results of home support services in Canada (Jetté & Vaillancourt, 2011).
The presentation above underscores the positive role of nonprofit organizations in coproduction of welfare services, and therefore arguably also obscures the more problematic issues.Despite this, there were articles that addressed some challenging aspects that could be related to nonprofit organizations and co-production.For example, one article discussed how co-production may co-opt nonprofit organizations to reproduce predominant government priorities rather that prioritizing stakeholder views (Kuts, 2002).Other articles highlighted the danger that nonprofit organizations may function solely as ordinary customer services (Ewert & Evers, 2014), that nonprofit organizations' disorganized character may affect coproduction negatively (Prentice, 2006), or that nonprofit organizations' participation in welfare reforms is mainly rhetoric (Fazzi, 2009).Research on co-production in general has also brought attention to some of the more problematical sides, such as the risks of coproduction excluding marginal groups in society (Brandsen & Helderman, 2012;Porter, 2012).

Distinctive Contributions
Out of the 59 articles included in the review, only 15 articles (25%) addressed the topic of nonprofit organizations making unique, distinctive contributions to co-production (Anheier, 2005;Hall, 1992;Salamon et al., 2000;Smith & Lipsky, 1993).I categorized three of the 15 articles (20%) as focusing on nonprofit organizations' role as essential to the very definition of co-production, seven articles (47%) as providing theoretical and empirical illustrations of distinctive contributions, and finally five articles (33%) as stating that nonprofit organizations to some degree, and under specific circumstances, may make distinctive contributions.In contrast to levels of co-production and the role of nonprofit organizations in co-production, the categories for analyzing the distinctive contributions were developed inductively.
Three articles addressed the topic of distinctive contributions by defining co-production as only or mainly related to the activities and characteristics of nonprofit organizations.For example, in the article, Coproducing Rural Public Schools in Brazil: Contestation, Clientelism, and the Landless Workers' Movement, the author defines co-production as, "the active participation of civil society actors in the provision of public goods" (Tarlau, 2013, p. 395).By referencing other researchers another article in the review notes, "that members of professional associations create and deliver much of the value enjoyed by the membership (i.e., 'coproduction')" (Hager, 2014, p. 415).Hence, co-production requires the participation of nonprofit organizations, and they deliver much of the value.A variation of considering nonprofit organizations as essential to co-production is an article discussing co-production mainly carried out by user organizations, such as self-help groups (Ewert & Evers, 2014).
Seven articles provided theoretical and empirical illustrations of distinctive contributions made by nonprofit organizations.One set of illustrations discussed the characteristics of nonprofit organizations, including for example the combination of a public purpose with the ability to involve users in a way that ensures the legitimacy of co-production in general (Lelieveldt et al., 2009) and how nonprofit organizations are more willing to diverge from core tasks to promote co-production (Strokosch & Osborne, 2017).Another set of examples related to user involvements.Nonprofit organizations were said to provide significant user involvement and control (Prentice, 2006), have a tradition in which users and staff co-produce the services together (Vamstad, 2012), and involve citizens individually as volunteers or collectively (Vaeggemose et al., 2018).One article also listed how nonprofit organizations were seen as ways to protect and promote individual and family choices, promote social cohesion, and offer bottom-up local control that builds community participation (Prentice, 2006).
Finally, five articles described how nonprofit organizations, to some degree, under specific circumstances, and-in comparison to public and for-profit organizations-made distinctive contributions.For example, nonprofit organizations are consulted to a higher degree on a range of policy issues (Lum et al., 2016) and deliver services that other organizations cannot easily provide (Lee & Han, 2016).Furthermore, in comparison to the private sector, nonprofit organizations are expected to be driven more by ideals and to be more participatory, democratic, and effective in promoting co-production (Bano, 2019).Even though the distinctive contributions of nonprofit organizations are acknowledged, one researcher argues that not all nonprofit organizations automatically can be equated with greater user participation (Pestoff, 2012).In a different article, the same researcher notes that the fact that nonprofit organizations are involved at different levels of co-production "may result in competing expectations about their role and what their distinctive contribution should be, both internally and externally" (Pestoff, 2014(Pestoff, , p. 1419)).

Findings and Discussion
There exists more research than expected on the role of nonprofit organizations in the coproduction of welfare services, as evidenced by the number of articles identified as part of this systematic literature review as well as their theoretical and empirical contributions.Even though a certain level of knowledge was expected, given the rising academic interest in matters related to co-production, it is still noteworthy that a review of literature-delimited to selection criteria related to co-production, nonprofit organizations, and welfare services-produces such a significant amount of research.I would therefore argue that this empirical result constitutes one of the main findings of this review.
In starting to review the research field in more detail, this article has presented the results of the coding of the included articles in relation to research characteristics, such as type of research approach and methodological orientation.For example, most articles relate to a European context, are primarily empirically oriented, and most articles use qualitative methods.These results obviously contribute to our shared understanding of what we know, that is the qualitative dimensions of empirical manifestations of co-production in Europe.At the same time, the categorization also indirectly indicates what we would need to study more, including, for example, co-production in other regions of the world as well as quantitative and comparative dimensions of co-production.There also seems to exist less knowledge production related to the analytical and theoretical side of co-production.
The article has also categorized the empirical material in relation to the framework for analysis.A way to analyze these empirical findings could be to compile these descriptions into a table that combines what I have conceptualized as levels of involvement and the role of nonprofit organizations (see Table 2).It should be noted that the compilation of what we know was firstly delimited to the 25 articles (42%) that I was able to categorize in relation to both levels and degrees of involvement.For comparative reasons, I also decided to omit the article that paid equal attention to enabling favorable conditions and providing organizational mechanisms as well as the three articles that paid equal attention to all three degrees of involvement.Thus, Table 2 is based on 21 out of 45 articles included in the review.
According to the compilation, research has so far primarily focused on how users and nonprofit organizations are involved in co-production and then co-governance and comanagement.Research has also to a greater degree studied how nonprofit organizations enable favorable conditions and then how they provide organizational mechanisms and deliver results.The two dimensions taken together specify that research to date mainly has focused on how nonprofit organizations enable favorable conditions, provide organizational mechanisms, and deliver results for co-production.At the same time, the compilation in Table 2 also indicates what we would need to study more if we are to understand the role of nonprofit organizations better and more comprehensively in the co-production of welfare services.These lesser-known areas include primarily nonprofit organizations' role in all three degrees of involvement in relation to co-management.We also need to pay more attention to the role of nonprofit organizations in providing organizational mechanisms and delivering results in relation to the co-governance and co-management of welfare services.
Moreover, I have also presented the degree to which articles included in this review have addressed the topic of distinctive contributions, that is if and, if so, to what degree nonprofit organizations make unique contributions to co-production.Based on this categorization I would argue that we know that some articles regard nonprofit organizations as essential to coproduction, that several articles provide illustrations of theoretical and empirical illustrations of distinctive contributions, and that some authors state that nonprofit organizations to some degree, and under specific circumstances, may make distinctive contributions.However, as only one fourth of the articles explicitly or implicitly addressed the topic, the notion of distinctiveness, nonprofit organizations, and co-production is an area that could be explored further in future research.
An area that also should be explored in more depth is similarities, differences, and distinctiveness between co-production implemented by nonprofit organizations, as they are manifested in this review of the literature, with co-production as implemented by public and

Not discussed
Nonprofit organizations considered essential to the very definition of co-production as well as make distinctive contributions for-profit organizations.For example, do nonprofit, for-profit, and public organizations engage in different types of co-production?Or in different policy areas?Even though these questions are outside the scope of this article, some preliminary insights could be formulated based on a comparison with published reviews of the literature related to public organizations (Clifton et al., 2020;Jukić et al., 2019;Rodriguez Müller et al., 2021;Voorberg et al., 2015).These insights are presented in Table 3.
Several critical remarks could be made in relation to the results of the review.First, as discussed in the presentation of the framework for analysis as well as in the presentation of results, it should be noted that the levels of involvement, the analytical role of nonprofit organizations in co-production, and the notion of nonprofit organizational distinctiveness are only to be considered as analytical devices and may therefore neither be mutually exclusive nor apparent in real world examples.Second, in addition to the dominance of qualitative dimensions of the role of nonprofit organizations in co-production in Europe discussed above, the variety of concepts for denoting matters related to the nonprofit sector, such as the third sector or civil society, questions the degree to which similar types of organizations have been studied.Third, there is a tendency in reviews such as this as well as in nonprofit research to underscore the positive sides of nonprofit organizations.Despite this, it should be noted that the review also identified articles that addressed some challenging aspects related to nonprofit organizations and co-production, including that nonprofit organizations' disorganized character may affect co-production negatively, among other things.There were also articles that, for example, argued that not all nonprofit organizations automatically can be equated with distinctive contributions to co-production.
It should finally be acknowledged that the results of this review are affected by the framework for analysis, the applied methodology as well as the acknowledged delimitations, including the selected databases, the terms used in the search string, and the demarcation to welfare services.For example, the field of welfare could be more regulated than other fields, mainstreamed by new public management and/or provide less room for differences among providers, that could serve as explanations to the results of the review.In addition, the results could be affected by the limitations of conducting a systematic review by only one researcher.
Thus, I cannot formulate conclusions beyond these limitations.However, the results of the review are in line with results from some other studies of a more overarching character (e.g., Benjamin & Brudney, 2018).Future research should not only explore areas that we know less about, such as the role of nonprofit organizations in the co-management of welfare services, but also review what the literature knows about the role of nonprofit organizations in the coproduction in other areas of society.

Conclusion
This article has explored what previous research knows about the role of nonprofit organizations in the co-production of welfare services by conducting a systematic literature review.The need for the review stems from the lack of comprehensive knowledge related to the role of nonprofit organizations in the co-production of welfare services as well as the fact that most previous systematic literature reviews focus on public organizations.Main contributions to the research field include that co-production should be associated with and researched in not only public organizations but also nonprofit organizations as well as the findings from the review.These findings include that research primarily has studied the role of nonprofit organizations in relation to co-production and enabling favorable conditions as opposed to co-management, co-governance, providing organizational mechanisms, and delivering results.Another contribution is the potential distinctive contributions of nonprofit organizations to co-production identified and studied in the literature.
These contributions have potential implications for practice, policy, and future research.Practitioners, in particular managers of nonprofit organizations, are encouraged to invite research that could study the degree to which users co-manage welfare services as well as if nonprofit organizations provide organizational mechanisms and deliver significant results related to co-production.Policymakers and politicians need to consider also nonprofit organizations to a higher degree in policies and regulations if they wish to promote coproduction in welfare services beyond public organizations.Future research, finally, should explore the results from this article in other fields and countries by using more comparative and quantitative methods.In particular, we would encourage research that would explore the potential distinctive contributions made by different types of organizations, including public, for-profit, and nonprofit organizations.

Table 1 .
Publication Year and Origin

2002 2005 2006 2007 2009 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Most of the articles are published in a wide range of different journals (45 different journals in total).Nevertheless, eight articles are published in Voluntas: International Journal of Voluntary & Nonprofit Organizations, three in BMC Health Services Research, three in Health Expectations, two in Public Management Review, and two in Social Policy & Administration.Furthermore, in the final selection of articles, there was an increase in the number of publications over the years.Ten papers were published during the first period

Table 2 .
Combining Levels of Involvement and the Role of Nonprofit Organizations

Table 3 .
Schematically Comparing the Results of This Review with Other Systematic Reviews Systematic Reviews on Co-