Evolution and Hotspots of Vocational Education and Lifelong Learning: A Visualized Analysis Using CiteSpace

3.1.1 Initial incubation phase (2005–2014)

During this first decade, the field was in its nascent stage. Annual publication figures remained consistently low, fluctuating marginally with minor peaks in 2009 (eight publications) and 2012 (thirteen publications), but with an average annual output of only seven publications. This pattern indicates that the interdisciplinary nexus between VET and LLL had not yet coalesced into a major, self-sustaining stream of international research. Scholarly efforts during this period were likely fragmented, focusing on foundational theoretical explorations or isolated case studies, without generating widespread, sustained academic momentum.

3.1.2 Rapid growth phase (2015–2017)

A dramatic inflection point occurred around 2015, when annual publications surged to twenty, effectively doubling the output from the previous year. This surge marked the transition to a period of rapid growth, with outputs remaining notably higher in 2016 (ten publications) and 2017 (sixteen publications) compared to the pre-2015 baseline. This remarkable ascent can be strongly correlated with the global policy landscape. The launch of the United Nations’ 2030 Agenda for Sustainable Development in 2015, which explicitly champions “inclusive and equitable quality education” and promotes “lifelong learning opportunities for all” (sustainable development goal [SDG] 4) [13], provided a powerful, universal mandate. Concurrently, in June 2015, the European Union (EU) released the 2015 Riga Summary, aiming to enhance the overall quality and status of VET within the context of the Copenhagen Process, thereby supporting broader European economic growth and employment initiatives [14]. Ongoing strategic initiatives in key regions, which linked VET to LLL strategies, catalyzed substantial policy-oriented and empirical research. This phase signifies the moment the topic gained significant traction on the international research agenda.

3.1.3 Consolidation and maturation phase (2018–2025)

From 2018 onward, the field entered a phase of consolidation. The data exhibit fluctuations but demonstrate a new, higher plateau of productivity, with an average of fifteen publications per year. This period is punctuated by new, significant peaks in 2022 (twenty-two publications) and 2024 (twenty-five publications), suggesting robust, sustained interest, and the emergence of new research sub-themes. The fluctuations likely reflect the field’s response to evolving global challenges, such as the imperative for digital skills and just green transitions in the wake of the Fourth Industrial Revolution, the assessment of National Qualifications Frameworks (NQFs), and the post-pandemic re-evaluation of online and blended learning models in professional training. It is noteworthy that the data for 2025 are provisional, given the current year is incomplete, yet the preceding high-volume years confirm the field’s continued relevance and dynamic evolution.

In summary, the analysis of publication output over the past twenty years reveals a compelling narrative of academic emergence and consolidation. The research domain concerning the integration of VET and LLL has unequivocally evolved from a niche interest into a mature and dynamically evolving field of international scholarly inquiry, firmly positioned at the intersection of global education policy, economic development, and social equity.

3.2.1 Institutional linchpin: Building bridges with qualifications frameworks

This theme represents the most critical structural foundation for the integration of VET and LLL. At its core, research in this area (Cluster 1: qualifications framework and Cluster 7: educational transition) investigates the systemic mechanisms that enable the recognition and portability of learning across time and contexts. The NQF is studied not merely as a classificatory tool but as a transformative “linchpin” that aims to break down the traditional barriers between academic and vocational pathways, as well as between formal, non-formal, and informal learning [15]. Scholars explore the design, implementation challenges, and governance of NQFs, examining how they can effectively standardize learning outcomes, ensure quality, and foster trust among employers and educational institutions.

This institutional architecture is intrinsically linked to the practicalities of learner mobility, as captured in Cluster 7. The focus on “educational transition” and the specific mention of a “credit-based lifelong learning system” highlight the operational tools that translate the theoretical promise of NQFs into reality. Research here delves into the development of credit accumulation and transfer systems, which allow individuals to build qualifications incrementally over their lifetimes. This facilitates vertical progression (e.g., from a vocational certificate to a university degree) and horizontal movement (e.g., between different trades or into new fields), thereby making the ideal of a seamless LLL journey a tangible possibility. The connection between these two clusters underscores a fundamental research consensus: without robust structural frameworks, the integration of VET and LLL remains fragmented and ineffective.

3.2.2 Core practice: Adult VET for labor market adaptation

This hotspot constitutes the practical heartland where the integration of VET and LLL directly impacts individuals and economies. It signifies a paradigm shift in VET, from a primary focus on initial preparation for youth to a continuous, lifelong process of skill development for adults (explicitly linking vocational training and adult education in Cluster 3). The research is rigorously anchored in the realities of the labor market (Cluster 5), analyzing how VET systems must adapt to macro-level challenges such as the skills demands of the Fourth Industrial Revolution [16], economic restructuring, and the need to reintegrate unemployed adults.

The economic underpinning of this practice is elaborated in Cluster 8 (education level). The keyword “human capital depreciation” is pivotal here, providing a powerful theoretical rationale for lifelong VET. Technological progress has a depreciation effect on human capital, rendering certain knowledge obsolete, even for highly skilled workers. This phenomenon is known as high-skill automation technological progress [17]. Schultz [18] and Becker [19] were the first to propose human capital theory, decomposing human capital into five components: healthcare facilities and services, on-the-job training, formal education, adult education programs, and labor migration. They emphasized that human capital serves as a vital source of technological innovation and economic growth, effectively driving sustainable economic and social development [18, 19]. Continuous investment in VET for adults is not a luxury but a necessity to counteract this depreciation, thereby maintaining individual employability and enhancing national economic competitiveness and resilience [20]. This body of work often involves empirical studies on the returns on investment in adult training and analyses of how VET policies can be designed to target specific skill gaps in the economy.

3.2.3 Drivers of change: Policy transfer and systemic reform

This thematic area moves beyond the “what” and “how” to investigate the “why” and “who” behind systemic integration; that is, the political and discursive forces that drive change. Research captured in Cluster 2 (institutional change) and Cluster 9 (international education policy) examines the complex processes of VET system modernization and adaptation. It explores the concept of “reform fit,” that is, how global LLL models are adapted, resisted, or transformed within specific national institutional contexts.

A significant focus is the role of supranational bodies, with the EU featuring prominently. Studies have analyzed the EU’s “mobile policies” and its strategic use of tools such as the “AQUA-TNET lifelong learning strategy” (Cluster 9) to foster policy convergence among member states [21–23]. The mention of “new EU member states” and “social dialogue” in Cluster 2 indicates a specific research interest in the dynamics of policy transfer to transitioning economies and the critical role of involving social partners (employers, trade unions) in the reform process [24, 25]. This research hotspot essentially investigates the governance of VET–LLL integration, viewing it as a politically negotiated and discursively constructed process.

3.2.4 Technological enabler: Digital integration of learning and training

This theme identifies digital technology not as a peripheral tool but as a fundamental enabler that reshapes the delivery and experience of integrated VET and LLL. The integration cluster (Cluster 6) is central here, with keywords such as e-learning, web, and technologies pointing to a robust research stream. Scholars have investigated how digital platforms, online learning modules, virtual simulations, and mobile technologies facilitate just-in-time, personalized, and accessible vocational training. This research moves beyond mere technical implementation to explore pedagogical models for blended learning (also in Cluster 0) [26], the development of digital competencies for both learners and trainers, and the potential of technology to create a ubiquitous “lifelong learning policy space” (Cluster 3), where learning opportunities are no longer constrained by geography or time [23]. It positions technology as the vehicle that can democratize access and make lifelong vocational learning a practical reality for diverse populations, including working adults.

3.2.5 Evolving frontiers: Competency assessment and contextual expansion

This final theme captures two critical and evolving frontiers of the field. First, the testing competence cluster (Cluster 0) addresses a fundamental challenge that arises from diversified learning pathways: how to validly and reliably assess and certify skills acquired outside traditional classrooms. Research in this area focuses on developing innovative assessment methodologies for complex competencies in environments such as blended learning spaces, community healthcare, and medical education [27]. It questions what constitutes valid evidence of learning and how to ensure that credentials issued through these new modes hold value in the labor market.

Second, the research hotspot cluster (Cluster 4) indicates significant expansion in both geographical scope and contextual dimensions within this field. The focus on China’s undergraduate vocational education and the case of Gujarat, India, demonstrates that discussions on integrating vocational education with LLL are becoming increasingly globalized [28]. This marks a shift in research perspectives away from a Eurocentric paradigm, with academia increasingly examining the interpretation, implementation, and localization of these concepts within major Asian economies and other distinct sociocultural contexts. This diversification enriches the field by introducing new paradigms, challenges, and empirical foundations.

4.1.1 Theoretical implications

First, this study has empirically validated and refined the conceptual model of VET–LLL integration. The three distinct phases identified in both the publication trends and evolutionary path, namely conceptual foundation, systemic integration, and value realization, demonstrate that the fusion of vocational education and LLL is not a spontaneous process but a deliberate, staged evolution. This progression, from establishing separate conceptual pillars to building institutional bridges and finally focusing on synergistic outcomes, provides a robust dynamic integration framework that can guide future theoretical development. It moves beyond abstract advocacy for integration to describing its concrete, measurable trajectory.

Second, the keyword clusters reveal that the integration is fundamentally multi-layered and systemic. The co-existence of distinct but interconnected clusters – qualifications framework (institutional layer), adult VET and labor market (practice layer), and digital integration (technological layer) – demonstrates that the field is structured as a complex ecosystem rather than a linear relationship. This finding challenges simplistic, one-dimensional models of VET–LLL interaction and calls for a more sophisticated, multi-level systems theory to fully comprehend the interplay between policy, practice, and technology in building effective LLL systems.

4.1.2 Practical implications

From a practical perspective, the findings offer clear guidance for policymakers and institutional leaders. The strong, sustained research focus on NQFs and Credit Systems underscores their non-negotiable role as the foundational infrastructure for integration. The implication for practice is unequivocal: strategic investments must prioritize developing and refining these transparent, skill-based recognition systems to dismantle barriers between education and work, and to make LLL a tangible reality for individuals.

Furthermore, the shift in research frontiers toward “skills,” “economic growth,” and “digital skills” provides a powerful narrative for advocacy and funding. It equips practitioners with evidence to frame lifelong vocational training not as a cost but as a critical investment in national competitiveness and individual employability. The demonstrated link between VET–LLL integration and macroeconomic outcomes, as seen in the latest burst keywords, is a crucial tool for securing political and financial support, urging a reallocation of resources toward upskilling and reskilling initiatives for the adult workforce.

Finally, the consistent emphasis on Germany and the EU as key nodes in the research network highlights the immense value of international benchmarking and policy learning. Rather than reinventing the wheel, educational leaders and policymakers are implored to systematically study, adapt, and implement proven models and policies from frontrunner countries and regions, thereby accelerating their own systemic integration processes.

4.2.1 The imperative of a unified NQF

The persistent prominence of the “qualifications framework” and its strong linkage to “educational transition” in the keyword analysis underscore its role as the foundational infrastructure for integration. Such a framework is crucial for recognizing and accrediting learning outcomes acquired through diverse formal, non-formal, and informal pathways. By establishing clear equivalence and transferability between vocational and academic credentials, an NQF can effectively dismantle institutional barriers, thereby creating a truly flexible and permeable LLL system that empowers individuals to navigate their learning and career trajectories seamlessly.

4.2.2 Strategic prioritization of adult and continuing vocational training

The convergence of clusters on “vocational training adult education” and “labor market,” coupled with the sustained burst of “adult education,” highlights that the core of the integrated system lies in serving the adult population. This provides a clear strategic direction: national policy and resource allocation must pivot toward strengthening and expanding continuing VET (CVET). This involves developing targeted programs for upskilling and reskilling the existing workforce, with a special focus on vulnerable groups, to proactively address skill obsolescence (human capital depreciation) and meet the demands of the evolving labor market, particularly those driven by the Fourth Industrial Revolution.

4.2.3 Leveraging digitalization as a core integrative enabler

The early emergence and sustained relevance of “e-learning” and the recent frontier of “digital skills” demonstrate that technology is not merely a delivery tool but is rather a transformative force for integration. This inspires a need to deeply integrate advanced digital pedagogy and infrastructure, particularly artificial intelligence (AI) and metaverse technologies, into the core of vocational education and LLL strategies. We should invest in large-scale, AI-powered digital learning platforms that can personalize learning pathways, provide real-time feedback, and automate assessment, thereby making LLL more efficient and accessible. Furthermore, the development of metaverse-based virtual campuses and simulation environments can create immersive, hands-on training experiences for vocational skills, from complex machinery operations to soft skills training, that are otherwise risky, costly, or impractical in the physical world. By systematically embedding not only foundational digital skills but also AI literacy and metaverse-enabled collaborative projects into all VET curricula, we can ensure equitable access to high-quality, future-oriented LLL opportunities.

4.2.4 Policy formulation through strategic international benchmarking

The strong research focus on “Germany” and the “European Union” indicates the significant value of cross-national policy learning. Rather than developing systems in isolation, we can gain immensely from a structured analysis of policy successes and challenges in established VET–LLL systems. This involves studying the mechanisms of their dual training models, governance structures involving social dialog, and the implementation of their qualification frameworks. Adapting these internationally validated practices to the specific socio-economic context of our country can accelerate the development of a robust and effective integrated system.

4.2.5 Aligning system outcomes with macro-economic goals

The powerful burst of “economic growth” as a recent research frontier provides a compelling narrative for justifying investment in VET–LLL integration. This insight should be leveraged to reposition lifelong vocational training in the national discourse, shifting it from social welfare expenditure to strategic investment in human capital and national economic competitiveness. Policymakers and educators should explicitly articulate and measure the contribution of VET–LLL initiatives to key macroeconomic indicators, thereby securing sustained political and financial commitment for building a highly skilled, adaptable workforce that drives sustainable development.