Green Marketing and Customers’ Purchasing Behavior: A Systematic Literature Review for Future Research Agenda

: With the rising concern for environmental issues, there is an ever-increasing demand for sustainable actions to minimize the damage to ecosystems. Seeking to meet such a demand, energy companies worldwide embrace green marketing solutions. This article aims to provide a comprehensive and systematic overview of green marketing and its impact on customers’ purchasing behavior to develop a research agenda that helps to identify promising areas for future research. We conducted a systematic literature review to ﬁll in the lack of conceptual clarity on the relationship between green marketing solutions and customers’ purchasing behavior. After compiling a candidate pool of 2604 papers and applying a set of inclusion and exclusion criteria, the ﬁnal sample comprised 166 articles published between 1995 and 2022. The results demonstrate that scholars frequently chose the energy sector to research green marketing’s impact on purchasing behavior. The review indicates that the theory of planned behavior with its progenitor theory of reasoned action seems to be highly featured. The literature emphasizes green marketing at the tactical level as impacting customer behavior measures at the purchase and post-purchase stages. Our study helps marketers to identify the best practices in the area to inﬂuence customers’ behavior effectively.


Introduction
The increase in world population and lack of environmental consciousness has determined unsustainable consumption patterns.Unsustainable consumption has caused severe environmental problems such as increased greenhouse gas emissions, pollution, global warming, and natural resource depletion [1,2].The rapid intensification of these problems raises the need for sustainability measures at every level of production, consumption, and general livelihood [2].Therefore, "sustainability has become the mantra for companies seeking to create a competitive advantage in the global marketplace" [3] (p. 118).
Due to Russia's invasion of Ukraine, energy prices have hit all-time highs.The impact of the war and sanctions on Russia as a primary supplier of gas to Europe has determined a 3-4-fold increase in energy prices [4].Under such circumstances, societies face the need for alternative and more ecological energy resources.The development and diversification of renewable energy sources have become fundamental issues of Europe's future attempts at sustainability and overcoming adverse climate changes.
Green marketing solutions have created a platform for sustainable consumption globally [1].Even though the concept of green marketing has been circulating for quite some time, it currently enjoys a revival in popularity in the business world [5].At the stage when customers' knowledge of renewable energy-related terms (such as renewable power, carbon footprint, and carbon offset) is increasing in scope and depth, businesses gain more pressure and opportunities to employ green marketing strategies [6].Organizations embrace green marketing challenges to meet their customers' ever-growing demand for Energies 2023, 16 sustainable consumption.Green marketing has gained considerable importance in the contemporary marketplace [1].This type of marketing provides a competitive advantage, improves organizational performance, and increases customer satisfaction [7,8].Green marketing solutions enhance customer behavior indicators, i.e., purchase intention and energy consumption [2,[9][10][11].
Even though research on green marketing and its impact on customer behavior has experienced vast growth in the number of publications in recent years, there exists a lack of conceptual clarity on the relationship between these two concepts.The absence of a detailed clarification of the impact of green marketing solutions on specific customers' purchasing indicators obstructs the exchange and development of scientific knowledge.It prevents marketers from finding out which green marketing solutions are the most promising in terms of customer purchasing behavior.Therefore, in this study, we raise the following research question: which green marketing solutions affect customers' purchasing behavior?To answer this question, there is a need for a review that analyses and synthesizes an existing array of studies in the field.In this respect, this research aims to provide a comprehensive and systematic overview of green marketing and its impact on customers' purchasing behavior to develop a research agenda that helps to identify promising areas for future research.The review utilized the PRISMA approach and covered 166 articles.These articles present the results of the studies that tend to remain largely isolated from the others.Considering the contextual differences between the studies, integrating their perspectives into a common framework can help to provide a holistic lens upon the green marketing phenomenon and its impact on customers' purchasing behavior.
In the background of systematic reviews on green marketing and its impact on customers' purchasing behavior, no research has categorized green marketing solutions based on the marketing planning horizon.The classification of green marketing practices as strategic, tactical, and operational green marketing solutions makes the study relevant, since the authors, based on this classification, were able to identify the impacted measures of customers' purchasing behavior on each level.
The theoretical and practical contribution of the current research can be summarized as follows: 1.
This paper presents a structured and comprehensive overview of research on green marketing and its impact on customer purchasing behavior.

2.
This paper synthesizes and categorizes the existing approaches to green marketing and its impact on customer purchasing behavior, which may help researchers to position their studies in the literature, and practitioners to find necessary topics.

3.
The paper predicts promising research gaps and develops an agenda for future research paths.
The remainder of the paper is structured as follows: Section 1 discusses the structure of green marketing solutions that may affect customer behavior.Aiming for a methodologically rigorous literature analysis, this section presents a conceptual framework.This framework will later be applied for the classification of the literature sample.The following section describes the methodology for the systematic literature review.A systematic literature review focusing on customers' purchasing behavior is conducted in Section 3. Based on the systematic literature review results, we have prepared a discussion, conclusions, and suggestions for future research in Section 4.

Conceptual Framework
Aiming to substantiate the chosen research approach, we present the conceptual background corresponding to the research question.In this regard, we discuss the development and scope of the green marketing concept; later, we move on to the potential of green marketing solutions impacting customer purchasing behavior.
The history of green marketing dates back to the 1960s when the wave of environmental concern led to ecological marketing.This wave was linked to the industries with the most damaging impacts.Since then, the general concept has been represented by such terms as eco-marketing, ecological marketing, sustainable marketing, and environmental marketing [5].
The scope and meaning of green marketing tend to be misinterpreted [5].Usually, it is limited to promoting green products [5,12]; however, green marketing involves many more components and activities to meet customers' green demands [13].Considering the previous research on green marketing [14,15], the definition that closely reveals the spirit of the concept explains green marketing as an "organization's participation in strategic, tactical, and operational marketing activities and processes that have a holistic objective of creating, communicating, and delivering products with minimal environmental impact" [15] (p.2).In this way, green marketing is concerned with a wide range of strategic, tactical, and operational activities.
At the strategic level, green marketing involves developing strategies to target and selectively appeal to environmentally conscious customers.Defensive or assertive strategies are available based on the prospected size of the green market and marketers' abilities to differentiate green products [16].
The tactical level of green marketing contains solutions related to the marketing mix that drives the organization towards sustainable marketing outcomes, creating value.It is a controllable marketing variable; therefore, the organization can consciously control its influence on customers [2].It means that product, pricing, distribution, and promotion must clearly emphasize environmental ideas.These marketing mix components become part of green marketing strategies to meet customer demands [7].
Green products may be slight modifications of existing products or truly new green products.The latter may become a source for the company's differentiation; however, at the same time, they are riskier [3].Green price demonstrated that environmentally sound products are more cost-intensive [5].The green place's credential resides in renewable energy usage in supply chains [6].According to Bañares et al. [12], green marketing strongly manifests its significance in advertising.Through advertising, business organizations communicate the environmentally friendly characteristics of their products [17].
At the operational level, green marketing focuses on attracting targeted environmentally conscious customers and efficiently completing the selling process [18].We suggest marketers concentrate not only on the efficient completion of the selling process, but also on delivering environmental and social values.
Usually, green marketing applies to business-to-customer (B2C) markets; however, Gelderman & Vijgen [19] have proven that this concept is appropriate in business-tobusiness (B2B) or business-to-government (B2G) settings as well.Within the strategic, tactical, and operational contexts, the green customer with his specific behavior in B2C, B2B, or B2G market appears.Green purchasing behavior in any of these markets is generally associated with purchasing in a sustainable, responsible, ethical, and environmentally friendly way.Adopting green behavior is a central facet of achieving sustainability [17].
Seeking to understand green customer behavior, the concept of purchase intention has been featured in a number of studies [2,9,20].Purchase intention is a crucial factor in predicting customer behavior [2].Green purchase intention is defined as customers' tendency to pay a price premium for a green product or brand [20].The increase in purchase intention shows that the possibility of purchasing a particular product by the customer increases correspondingly [2].It means that marketers must develop marketing solutions that are green in nature to encourage the increase in purchase intention to grow into a purchase decision.However, it is essential to mention that the intention does not always translate into actual purchasing behavior [10,17].If it translates, there is an opportunity to segment the customers based on their actual behavior.For example, Paço & Varejão [10] suggest segmenting customers who use electrical household appliances and other electrical equipment, air conditioning, and lighting based on their energy-saving behavior into savers and non-carers.
As the research object, green marketing follows two approaches in terms of impact.The first approach focuses on the green marketing influence on customer purchasing behavior, while the other systematizes the possible effect on the organization (with or without customer purchasing intention as a moderating/mediating variable).This research considers both approaches, with a relevant condition for the second approach.The studies representing the latter approach shall be included in the systematic literature review only if they involve any variable of customer purchasing behavior (as a dependent, moderating, or mediating variable).

Materials and Methods
Having analyzed the conceptual approaches to seeking desirable customers' purchasing behavior with green marketing, we now focus on the articles in the field to examine the links between green marketing and customers' purchasing behavior.For this reason, we have chosen to conduct a systematic literature review in the paper at hand.A systematic literature review is a robust, rigorous, and transparent method that allows one to examine a corpus of scholarly literature and develop critical reflections, insights, future research questions, and paths [21].
The research aims to provide a comprehensive and systematic overview of green marketing and its impact on customers' purchasing behavior to develop an agenda that helps to identify promising areas for future research.This study includes existing papers that met the selection criteria defined in this paper without any limitations on the year of publication.The paper employs a conceptual framework that covers all the relevant stages of the literature-selection process (Figure 1).The research used the PRISMA approach which presents clear step-by-step instructions for a systematic way of reviewing literature.
Following the methodology of a systematic literature review described in Patticrew and Roberts [22], and applied, for example, by Kostagiolas and Katsani [23], Khan, and Qureshi [24], we systematically searched the literature to identify the articles that cover the problems of green marketing and its impact on customer purchasing behavior.Three databases, namely Scopus, Web of Science, and EBSCOhost, were searched using the following keywords: "green marketing", "customer behavior", "consumer behavior", "purchasing behavior", "purchasing intention", "consumption", "buying", "purchasing", "green purchase", and "green consumerism".The combination of three databases prevents possible shortcomings of one database.The search in the databases was addressed to papers containing at least one combination of "green marketing" and any other keyword from the list in their title, abstract, or keywords.Only papers in English that appeared in peer-reviewed academic journals were considered relevant.We refrained from analyzing other publication outlets such as monographs, books, book chapters, commentary essays, conference proceedings, and letters to the editor.Searches were performed on May 2022.
Papers with a different content focus (e.g., demarketing, conventional marketing) or works that did not present empirical evidence were excluded from the analysis.An initial search resulted in many papers not specifying the possible relationship between green marketing and customer purchasing behavior in the title, abstract, or keywords.We manually screened the titles, abstracts, and keywords to determine whether the identified papers addressed our research problem.In particular, we eliminated duplicate articles.We also have decided to exclude literature reviews from the analysis.
The first evaluation condensed the literature sample to 254 papers.After reading the contents, we reduced the working sample to 166 relevant research articles.We have created an Excel workbook for records of primary data of the 166 articles that formed the evidence base of the review.The first evaluation condensed the literature sample to 254 papers.After reading the contents, we reduced the working sample to 166 relevant research articles.We have created an Excel workbook for records of primary data of the 166 articles that formed the evidence base of the review.

Characteristics of the Body of the Literature
The database search led to 612 initial hits in Scopus, 419 in WoS, and 1573 in Business Source Premier.After the first screening procedure for relevance in light of the chosen selection criteria and the elimination of duplicate papers, 254 papers remained in the initial sample.All the documents of the working pool were utterly read.Examining their contents led to a further exclusion of 87 articles and a final sample of 166 studies.
Figure 2 presents the number of sampled papers published every year.The first studies on green marketing and its relationship to customer behavior were published in 1995

Characteristics of the Body of the Literature
The database search led to 612 initial hits in Scopus, 419 in WoS, and 1573 in Business Source Premier.After the first screening procedure for relevance in light of the chosen selection criteria and the elimination of duplicate papers, 254 papers remained in the initial sample.All the documents of the working pool were utterly read.Examining their contents led to a further exclusion of 87 articles and a final sample of 166 studies.
Figure 2 presents the number of sampled papers published every year.The first studies on green marketing and its relationship to customer behavior were published in 1995 (the work of Shrum et al. [25]).The trendline highlights the increasing research output in this field.On average, six articles per year were published during 1995-2022, with the years 2019-2021 being the ones with the highest productivity.
(the work of Shrum et al. [25]).The trendline highlights the increasing research output in this field.On average, six articles per year were published during 1995-2022, with the years 2019-2021 being the ones with the highest productivity.

Researched Settings
The selected papers are not evenly distributed across the continents in terms of researched settings.Most of them cover Asia (62.57%), with some participation from the remaining continents.The dominant position of Asia is undoubtedly related to the rapid growth of overall research activity in this continent since 2000 [26].The papers' distribution across the continents has shown that 19% of studies were conducted in Europe and 8% in North America.
The research was carried out in 45 countries (Figure 3), distributed as follows: India with 21 studies; Malaysia with 14 studies; the United States of America with 12 studies; Pakistan and Taiwan with 11 studies each; China with ten studies; Indonesia with nine studies; Iran with eight studies; South Korea with seven studies; Vietnam with six studies; Portugal with five studies; Australia, Spain, Sweden, and the United Kingdom with four studies each; Ghana, New Zealand, and Romania with three studies each; Brazil, Canada, Netherlands, Slovakia, South Africa, Bangladesh, and Thailand with two studies each; and Algeria, Bangladesh, Brazil, Cambodia, Croatia, Egypt, France, Germany, Greece, Hong Kong, Italy, Kingdom of Bahrain, Malaysia, Mauritius, Poland, Saudi Arabia, Switzerland, United Arab Emirates, and Austria with one study in each country.Some studies (3.01%) were conducted in more than one country.
Studies on green marketing have been conducted in different sectors and industries (Table 2).Scholars conducted the most research (97.59%) in B2C markets; only four studies (2.41%) were devoted to analyzing green marketing's impact on purchasing behavior in B2B markets.Approximately one-third of the studies (52 or 31.33%)were not devoted to one particular industry.Some studies focused exclusively on the energy sector and aimed to ex-  Approximately one-third of the studies (52 or 31.33%)were not devoted to one particular industry.Some studies focused exclusively on the energy sector and aimed to explore various facets of energy consumption (Table 3).For example, Sammer, Wüstenhagen [27], and Mydock [6] confined the analysis to the products subjected to an energy-labeling scheme.The list of such products consists of energy-efficient appliances such as washing machines.Some studies [10,11] were devoted to evaluating green marketing on energy Energies 2023, 16, 456 9 of 20 consumption behavior, particularly energy saving.Other researchers [28,29] envisaged the risks of greenwashing in energy companies and the possible negative impact of greenwashing on customer behavior.Considering the array of green marketing studies in the energy sector, we state that this marketing is relevant and influential when the problem of depletion of finite energy resources is so essential.Table 3. Theories/models explaining the impact of green marketing on customer behavior.

Theory/Model Basic Ideology Green Marketing Rationale Representative Research
Theory of planned behavior (TPB) Attitudes, subjective norms, and perceived control of individuals are the predictors of behavior.
The theory is capable of investigating internal factors that influence green purchasing behavior.
The theory is capable of investigating internal factors that influence green purchasing behavior. [

Stimulus-organismresponse (SOR) model
The framework consists of three elements: stimulus, organism, and responses.Stimulus is associated with any environmental factor eliciting internal relations between an individual and the environment.Organism describes the structures and internal processes that intervene between individuals' final actions, responses, reactions, and external stimuli.The response is the customers' approach or avoidance.
Stimulus elements are eco-labeling and green advertising.They may have an impact on green customer-based brand equity.Organism elements may be green perceived quality, green image, and green trust.Purchasing intention falls into the response element. [39,58-60]

Environmentally conscious consumer behavior (ECCB) model
The theory examines the reasons for behavior.Under this approach, cognition determines the act, which in turn has an impact on behavior.
The predictors of green purchase intention may be an acceleration of greenwashing, green skepticism, and customers' knowledge.
Green perception and marketing strategy may change customers' perception of cognition-affect-behavior models over time.[31,52] Attribution theory The theory explains causal relationships in human activities.The theory expounds on the objective of the organization and discusses how organizational behavior impacts customers' attitudes and behaviors.

Green marketing objectives in corporate settings have an influence on customer attitudes and behaviors
based on customers' perceptions.
[ 64,65] Four forces model It is a structured approach that explains the cause, need, and process of sustainable development.The four main forces are customers, legislation, economic benefit, and community.
The model is the basis for engaging in the process of greening.To achieve sustainable development, the organization has to pass green marketing.The theory provides sufficient background to expect that customers will evaluate the accuracy of the promotional message and the credibility of its source.[10,11] Table 3. Cont.

Regulatory focus theory
Different motivation systems govern individuals' drive to reach the desired outcomes.Promotion-focused people concentrate on aspirations and achievements, and desired goals and life events fall into a set of gains and non-gains.Prevention-focused people tend to be vigilant and safe.For them, goals and life events fall into losses and non-losses.
Behavioral intentions regarding green marketing messages may differ among customers having different regulatory focus.[66,67] Signaling theory The theory concerns how the information is represented in signals and transmitted from the sender to the receiver.
marketing communication is a signal that reduces customers' apathy toward product information.Eco-labeling increases the confidence and credibility of green marketing claims, and improves trust.[56,59] Value-belief-norm theory The theory explains individuals' responses to environmentalism and concerns about how individuals' values lead to beliefs, subsequent norms, and purchase intentions.
The relative effect of altruistic behavioral orientation and economic orientation have an impact on customers' green purchase intention. [68] From the 166 articles analyzed, 154 (92.77%) applied a quantitative approach to research the chosen settings, four (2.41%) a qualitative one, and eight (4.82%) combined both approaches.Although data collection in most empirical research was quantitative-led, usually applying surveys, we have also found focus groups, interviews, and discourse observations among the pool of methods.The chosen participants in many cases of researched settings were customers, while others used students, family members, and friends.Participants' numbers ranged from 10 to 3264 (254 on average).Quantitative and qualitative or mixed studies contained specific theoretical approaches.

Theoretical Approaches Explaining the Impact of Green Marketing on Customer Behavior
This section summarizes different theoretical approaches toward desirable customer behavior with green marketing.We investigate theoretical reasoning in customer behavior theories concerning approaches to green marketing, enabling us to determine the biases and possible development directions of green marketing research.
Of the 166 documents, 66 (39.76%) provided a theory or model explaining customer behavior and green marketing as its antecedent.The remainder of the articles discussed green marketing's impact on customer behavior without explicitly choosing the theory or model (Table 3).
The theory of planned behavior is the most famous theoretical perspective on customer behavior in green marketing.This perspective considers attitudes, subjective norms, and perceived behavioral control as predictors of customer behavior.Although the recent marketing literature [69,70] criticizes the theory of planned behavior, this framework has profoundly influenced the evolution of customer behavior literature.Green marketing tools through the lens of the theory of planned behavior were introduced in the study by Testa et al. [45].The authors focused on the effectiveness of one particular green marketing tool, eco-labeling.Since then, the popularity of the theory of planned behavior has been gradually increasing.For example, in a recent research, Ch et al. [8] emphasized that the theory of planned behavior strongly supports green purchasing behavior.
The other theoretical perspective, the theory of reasoned action, was also widely employed for research into adjusting customer behavior through the tools of green marketing.We have accumulated evidence of the use of this theoretical foundation in the studies of the impact of eco-labeling [45], green appeal [47], perception of green products [49], etc.The repeated applications of the theory of reasoned action are related to the aforementioned theory of planned behavior, as the theory of reasoned action originated as an improved version of the theory of planned behavior.
The other scholars have chosen stimulus-organism-response, cognition-affect-behavior, environmentally conscious customer behavior, four forces models, attitude-behaviorcontext, attribution, regulatory focus, or value-belief-norm theories as conceptual frameworks.Most research was based on one theory, but some scholars combined two or more theoretical perspectives.For example, Liao [56] confirmed that the combination of signaling and attitude-behavior-context theories could explain the moderation of green marketing on customers' purchase intention.However, some authors [2,68,69] did not exploit any theories.

Green Marketing Impact on Customers' Purchasing Behavior
The researched factors of green marketing compound three main categories based on the levels of green marketing.The first level describes the actions of green marketing exclusively from a strategic perspective.The second level focuses on tactical solutions commonly related to the marketing mix.The third level demonstrates the orientation toward operational actions in green marketing.Scholars chose these levels to research as a solitary focus or combined with the other levels (Table 4).Many of the included documents focus on tactical green marketing's impact on customer behavior.The most common standard approach is to reveal tactical green marketing through the product (for example, energy labeling and cleaner production) or promotion (for example, green campaign and media exposure) (Table 5).
Table 5.The green marketing factors that have an impact on customer behavior.

Promotion
Green advertising (design, advertisement credibility, appeals, skepticism), message (type, the use of sentiments, credibility), sources of marketing communication, media formats, green viral communication, green campaign, communication involvement, receptivity to green communication, media exposure [17,20,46,58,62,67,78,[88][89][90] Processes Care in shopping, green procurement [3,25] Operational Salesperson's green expertise, eco-servicescape, point of purchase information [19,85] Twenty-one of the reviewed papers (12.65%) used an entirely strategic approach to green marketing.It means that the development of branding, reputation, green marketing awareness, green design, green positioning, waste marketing, green integration, green management, greenwashing, image, perception, policy, strategic green marketing orientation, and strategies is a common practice to achieve the desired customer purchasing behavior.
By implementing strategic, tactical, and operational green marketing solutions, companies contribute to the desired customer behavior.The studies reviewed presented the relationships between green marketing solutions and key variables of customer behavior.Considering the wide variety of the variables, we have chosen to classify them based on the customer decision process and the theory of planned behavior (Figure 4).Traditionally, the customer decision process starts with need recognition, then passes to the stages of information search and evaluation, and ends in the stages of purchase and post-purchase [91].Customer behavior metrics employed in the studies fall into the last two phases of the customer decision process.The purchase stage covers behavioral intention and actual behavior.
The studies reviewed confirm the relationships between green marketing and intentions measured as an intention to behave in an environmentally friendly manner, intentions to support a brand or organization, purchasing interest, product preference, green purchase intentions, and intentions to pay a price premium.The studies also register positive impacts of green marketing solutions on customer behavior towards the environment, energy-saving behavior, purchase behavior, and consumption level.Regarding the relationship between green marketing solutions and key variables of post-purchasing behavior, the studies analyzed show the increase in customer loyalty towards the brand, green product, green-oriented store, or green organization.
Based on green marketing research, we could find out the specific impact green marketing factors at different levels have on customer behavior measures (Table 6).It was found that promotion as an element of tactical green marketing has an immense potential to impact customer behavior measures.

Discussion
Green marketing solutions enhance various indicators of customer behavior; however, to date, there has been a lack of a detailed specification of how strategic, tactical, and operational green marketing practices affect customer behavior at different stages of the customer decision process.To unlock this puzzle, we aimed to provide a comprehensive and systematic overview of green marketing and its impact on customers' purchasing behavior to develop a research agenda that helps to identify promising areas for future research.We reviewed a large body of literature with the chosen systematic literature review methodology.We explored the past 28 years of research concerning the impact of green marketing on customer behavior.Even though we have reviewed a large number of existing literature on the effect of green marketing on customer behavior, there may still be papers that were not examined in this study.Since the last time we conducted a search was May 2022, it is likely that some 2022 papers on this topic were not included.
After the comprehensive review of articles included in the analysis, we categorized green marketing factors into three categories based on the levels of green marketing.The most common viewpoint to green marketing initiatives is bounded by the tactical level of green marketing, particularly promotion.However, green marketing is not only about the promotion of green products; it is a strategy, as well-a strategy that implies a radical change in the vision to lead organizations and not only to generate profits through desirable consumption behavior [92].
In the literature, there are definitions of purchasing behavior that explain the concept as the customer's search, purchase, usage, appraisal, and disposal of products, services, or ideas in order to satisfy their needs [93] (p.1682).With regard to measuring customers' green purchasing behavior, we have identified the metrics that fall into two categories based on the stages of the traditional customer decision process, i.e., purchase and post-purchase.Green marketing at the strategic level increases purchase interest, product preference, purchase intention, purchase behavior, consumption level, loyalty towards green products, and green-oriented store.Regarding the green marketing solutions at the tactical level, we have noticed that green product and green promotion impact the widest variety of customer-purchasing measures, while the impact of green processes manifests in purchasing behavior.In the studies reviewed, any combination of green marketing solutions at different levels did not seem as powerful as initiatives implemented on one specific level.Therefore, we assume that the synergy of green marketing solutions representing more than one level may not strongly impact customers' purchasing behavior.However, a short list of measures may not mean a slighter impact; the impact may be strong but not diverse in terms of measures.Additional empirical evidence is required to determine how different combinations of green marketing solutions representing strategic, tactical, and operational levels affect customers' behavior at the purchase and post-purchase stages.Therefore, the authors of this paper commit to carrying out an empirical study in European countries to test the possible relationships between green marketing solutions and customers' purchasing behavior.
At the purchase stage, green marketing solutions influence intentions and actual behavior.However, we have to note that "the intention to purchase does not always translate into actual purchase behavior when consumers are confronted with a purchase situation" [91] (p.423).This means that there may exist a gap between planned and actual customer behavior.In such a way, the possible impact of green marketing may end at the intentions without proceeding to the actual and post-purchase behavior.Despite this limitation, most reviewed studies confirm that green marketing is a reliable and essential tool that significantly impacts customers' purchasing behavior in the challenging business environment.
The other limitation of this systematic literature review is related to the choice to concentrate exclusively on behavioral indicators.According to the theory of planned behavior, an important antecedent of behavioral intention is attitude.In the researched sample, there were studies [62,89,[94][95][96] that involved attitudinal indicators (attitude towards the green purchase, attitude towards the advertisement, brand attitude, etc.) next to the behavioral ones.However, this systematic literature review did not cover them as they fall out of the scope of behavioral indicators.However, the authors of this paper endorse the impact of attitudinal measures in aiming for desirable customer behavior.
The systematic literature review is limited in the choice of databases (WoS, Scopus, and EBSCO).Including other databases, for example, ProQuest, Springer, ScienceDirect and others, could contribute to the search for studies on green marketing and its impact on customers' purchasing behavior.However, the chosen three databases assured the research area's reliability.With this limitation in mind, we recommend that future studies in the analyzed field include more databases (for example, ProQuest, Springer, and ScienceDirect) and search engines (for example, Google Scholar and Microsoft Academic).
One more limitation of the systematic literature review on green marketing and its impact on customers' purchasing behavior is that this review does not present the quantitative results of a meta-analysis.However, the collected amount of data regarding the effect of green marketing solutions on customers' purchasing behavior is vast, and the authors of this paper consider the possibility of using this data in the future for a thorough meta-analytic structural equation modeling study of green marketing factors affecting customers' purchasing behavior.
The results of our literature review suggest the following research recommendations: 1.Much of the existing research supports green marketing only at the strategic or tactical level.We assume that more studies should adopt green marketing at more than one particular level.A demand exists for an integrated view of green marketing to maximize the impact on customer purchasing behavior.

2.
In light of an increasing number of works on green marketing and its impact on customer behavior, the topic seems to be under-researched in terms of the following sectors: industrials, health care, financials, utilities, and real estate.

Conclusions
This review extends the existing literature on green marketing and its impact on purchasing behavior by providing an exhaustive overview of studies that developed the clarification of paths between strategic, tactical, and operational marketing, and customer behavior measures at different stages of the customer decision process, and it may support scholars in finding promising angles for future research.
Aiming to provide a comprehensive and systematic overview of green marketing and its impact on customers' purchasing behavior to develop a research agenda that helps to identify promising areas for future research, we suggested a framework of green marketing based on the strategical, tactical, and operational levels, and then categorized customer behavior measures depending on green marketing levels.Subsequently, papers that were found in databases were assigned to the identified categories.The analysis of 166 articles has shown that green marketing in terms of purchasing behavior has attracted vast attention during the last decades, with publication numbers increasing enormously after 2010 (over 96% of the sampled articles were published after 2010).Our review has indicated that the energy sector was frequently chosen for the research in green marketing's impact on purchasing behavior.Most sampled papers featured a theoretical approach based on the theory of planned behavior or its progenitor theory of reasoned action.
Our review shows that green marketing at the tactical level was often addressed as impacting customer behavior measures at the purchase and post-purchase stages.The most frequently affected customer behavior measures are green purchase intention and purchase behavior.
Even though the paper at hand has used a scientifically rigorous research methodology, our study has some limitations.First, the literature review sample was limited to articles published only in peer-reviewed academic journals.Including book chapters or conference proceedings may have resulted in additional important studies and insights.Similarly, the chosen keywords may have led to the exclusion of possibly relevant studies.

Figure 1 .
Figure 1.Flowchart of the literature-selection process based on the PRISMA approach.

Figure 1 .
Figure 1.Flowchart of the literature-selection process based on the PRISMA approach.

Figure 2 .
Figure 2. The number of papers published per year.

Figure 2 .
Figure 2. The number of papers published per year.The articles were published in 120 different journals.Table 1 offers an overview of the academic journals that published papers containing the final sample.Sustainability published the most significant number of relevant studies.Marketing Intelligence & Planning, British Food Journal, Business Strategy and Environment, Electronic Green Journal, International Journal of Environmental Research and Public Health, Journal of Advertising, Journal of Cleaner Production, Journal of Retailing and Consumer Services, and Journal of Strategic Marketing are the other popular outlets for the research in green marketing.Such diversity in journal coverage reflects the interdisciplinary nature of green marketing and customer behavior.The broad nature of sources taken into consideration and not relying exclusively on marketing sources increases the credibility of a systematic literature review.A. Paco and N.M.Suki were the authors who published the highest number of studies in the area of green marketing and customer behavior, with three records each.Fourteen other authors (A.A. Bailey, V. Bathmanathan, AB.C. Castro, Y.S. Chen, Y.R. Chen, D. Jaiswal, L.W. Johnson, A.S. Mishra, T.T. Pham, J. Rajadurai, V. Sethi, K.T. Smithy, M.F.Tiamiyu, and L. Varejeo) published two studies each.

Energies 2023 , 20 Figure 3 .
Figure 3. Countries of research locations (the colors indicate the intensity of studies).

Figure 3 .
Figure 3. Countries of research locations (the colors indicate the intensity of studies).

Figure 4 .
Figure 4.The researched paths between green marketing and customers' purchasing behavior.Figure 4. The researched paths between green marketing and customers' purchasing behavior.

Figure 4 .
Figure 4.The researched paths between green marketing and customers' purchasing behavior.Figure 4. The researched paths between green marketing and customers' purchasing behavior.

Table 1 .
The number of papers published per journal.

Table 1 .
The number of papers published per journal.

Table 2 .
The researched products (classification based on The Global Industry Classification Standard).

Table 2 .
The researched products (classification based on The Global Industry Classification Standard).

Table 4 .
The distribution of research across green marketing levels.

Table 6 .
The researched paths between green marketing at different levels and specific customerbehavior measures.