“Do as I say, not as I do” - a systematic literature review on the attitude-behaviour gap towards sustainable consumption of Generation Y

This paper contributes to a consolidation of the field by narrowing down the gap between sustainable consumption “attitudes/intentions” and actual consumption “behaviour”. The adopted methodology is based on a systematic literature review with an initial sample of more than 1000 publications, this paper considers the following inclusion and exclusion criteria throughout the review: research scope, conceptualisation of the terms (e.g. “Sustainable consumption”; “Ethical consumption”; “Green consumption”; “Green consumerism”; “Responsible consumption”), research design (e.g. quantitative, qualitative experimental studies), segments of consumers (Generation Y) and time frame. A qualitative research approach will be adopted in this paper, to safeguard the inclusion of methodologically diverse studies. Additionally, because the mentioned concepts have evolved over time and raised so many different interpretations, a qualitative approach is considered more pertinent. The focus of the review is to build up coherence regarding the sustainable consumption attitude-behavior gap. The paper concludes with a discussion of challenges and recommendations for future work in the field, namely, the need to encourage and educate consumers to live a more sustainable lifestyle and to design and implement responsible marketing tools to communicate the value of sustainable consumption.


Introduction
A consequence of the growing number of conceptual and empirical studies in sustainable consumption is the need to adopt systematic approaches to evaluate and assemble research outcomes that provide a balanced and objective summary regarding a particular topic. The paper reports on the adoption of such approach -systematic literature review -to the published studies relevant to topics within the sustainable consumption domain. So far, research on sustainable consumption is scattered across different disciplines and lacks integration, giving raise to many different definitions of the concept. Research into the responsible, ethical, sustainable, green and socio-political aspects of consumption has grown considerably since the 1990s. The most consistent finding within this literature has been inconsistency between what people say and what they actually do -the so-called "attitude-behaviour" and "intention-behaviour" gaps [1][2][3][4][5].
For instance, in a study of the Millennial generation, [4] observed that even though consumers have a very positive attitude towards sustainability and green products, this attitude is not reflected in actual behaviour. That way, it is of true importance, the understanding of consumers and what influences them. Every consumer is an important part of the fashion system, thus creating a valuable influence in the pursuit of sustainability in the fashion industry. There are several aspects to consider when analysing fashion consumers and sustainability: the consumer knowledge about sustainability, consumer behaviour and consumption habits and feelings associated with sustainable consumption. In 2 fact, the attitude and the behaviour of consumers are in line with the rapid production. Encouraged by low prices and influenced by marketing campaigns and trend changes, consumers tend to speed their fashion consumption [6]. These younger consumers, called the generation Y (Millennials), are defined as a group of people born between 1980 and 2000 [7] and maintain a positive attitude in relation to sustainability in general. However, there is a clear contradiction between how Millennials think about sustainability and what they do when it comes to a sustainable consumption [8]. According to [9], one possible justification for the existence of this gap lies in the consumers' lack of awareness of how their consumption can contribute to the environmental and social problems. Consumers also tend to shift the blame of the current sustainability issues to other institutions like businesses, education and society or even refuse to accept their contribution in the problem itself. There are several efforts required in the areas of innovation, recycling and conservation that could develop a more sustainable consumption way of life on a global scale [10]. A positive attitude is the key to a positive behaviour, therefore it is of true importance that consumers are informed and educated about sustainable consumption and how their behaviour can influence the pursuit of sustainability [11][12][13].

Methodology
This paper reports on a work-in-progress endeavour aiming at developing a comprehensive review of current knowledge in this area since the 1980s. The study adopts the systematic literature review methodology to clarify diverse and confusing theoretical frameworks regarding the so-called attitudebehaviour gap of millennials in respect to sustainable consumption. Although originally developed and employed in medical and health care studies, SLR are gradually gaining momentum in the social sciences, particularly, in management and business fields [14,15]. The reason for taking this particular methodology is that this field lacks clarity and consensus. By systematically reviewing the literature, we are able to synthetize existing literature and empirical evidence in a transparent and replicable way, identify areas where knowledge is still scarce and point out future research questions to academics, practitioners and policy makers [16,17]. This paper reports on the first stage of this SLR. From a range of 1079 papers in total, we identified 128 papers that need to be thoroughly revised. Given that this paper reports on a work-in-progress, it limits itself to the analysis of 26 studies focused on four key concepts: sustainable/green/ethical consumption, attitude-behaviour gap among millennials, fashion consumption and finally, the characterization of Generation Y/Millennials.

Data collection:
Studies were identified by searching three electronic databases -Web of Science, Scopus and Google Scholar -using a combination of key words, search strings (AND and OR) and root terms, e.g. Sustain* Consum* to include all studies using the words sustainable and sustainability, consumers, consumer, consumption, consumerism, etc. Table 1 presents the array of combinations searched and reproduced in the three databases, from more complex strings to simpler combinations. 2. Study selection and data extraction: Criteria to include and exclude studies were defined and applied to the set of 1079 papers: studies published after 1990 in order to grasp the millennials attitudes only, written in English, empirically based on millennials consumption behaviour, and initially, focused on fashion or apparel purchases only. As this criteria was too narrowing, we opened the search to other types of products and services in order to grasp millennials attitudes towards green, sustainable or ethical consumption, in general. After discarding duplicates, within and across databases (196 in total), 983 titles and abstracts were first extracted to a data sheet and thoroughly reviewed and analysed. This process resulted in 128 potentially relevant articles to include in the final SLR, from which 26 are reported in this paper. The steps of data selection and extraction are reported in During the selection process, studies focusing only on the supply side of green, ethic or sustainable products/services were excluded, given that the focus of this study is on the demand side, particularly from millennials. Hence studies dealing companies' sustainability strategies or corporate social responsibility or corporate green strategies, were discarded. Studies dealing with green marketing or green supply chains, in general, were also excluded. For each study, data from full texts were extracted, including author(s), publication year, title, key words, research questions, methodology and main results. These were subject to thematic analysis, giving place to four main themes discussed in the following section.
3. Analysis and discussion: key concepts defined 3.1. Sustainable/green consumer behaviour: A large body of literature deals with green, or sustainable, consumer behaviour. These terms are used interchangeably in most of the articles reviewed. This concept is interpreted as an improving pace of consumption that thrives to minimize the depletion of natural resources for future generations, by changing consumers' habits in their purchasing, use and recycling behaviour [12]. It involves the study of the various procedures that individuals, groups or organisations adopt to buy, use and dispose products/services/experiences to meet their needs and the impact of these behaviour on society. Research on the topic started in the 60s by characterizing green and conscious consumers in terms of their socio-demographic features and personality traits. Later on the concept of consumers' pro-environmental attitudes and values was brought to the debate to explain the differences between an eco-centric/biospheric value orientation and an anthropocentric/altruistic value orientation. While the former translates consumers that seek to protect Nature, the latter translates consumers who seek to protect Nature to provide a clean environment for humankind [11]. Attached to green or sustainable consumption, studies also discuss consumers' doubts regarding sustainable brands' credibility and greenwashing that is companies positioning themselves as "green" although they do not behave in a sustainable manner [18].

Attitude-Behaviour gap in green/sustainable consumer behaviour:
Given than presently the estimated market share of green products is less than 4% worldwide [28,29], researchers call for the need to understand consumers' motivations, concerns and values and design strategies to stimulate green consumption and promote environmental consciousness. As emphasized in the literature, it is difficult to influence behaviour without first impacting attitudes and values, particularly when claims and attitudes may not always translate into actual behaviour [19]. Various attitude-behaviour models have been developed to explain pro-environmental consumer behaviour, namely, the theory of reasoned action [21], the extended theory of planned behaviour [22], the theory of underlying personal and cultural values orientations [23]. The common denominator in what green purchasing is concern, Aegean International 4 is that consumers who claim themselves as pro-environment try to purchase only green products [24,25] and are truly committed to engage in efforts to solve environmental problems claiming their willingness to contribute personally to their solution [26]. The concept of self-identity is also suggested as a good predictor of green/sustainable consumption behaviour and an empowering approach to explain the attitude-behaviour gap of Gen-Y consumers [27].

Fashion industry's impact on sustainability:
Fashion industry is defined in the literature as the set of "companies and individuals involved in the creation, production, promotion, and sale of items that (a) have novel and specific aesthetic and functional properties, (b) trigger psychological reactions related to desire and need, and (c) are adopted by a group of people for a limited amount of time" [12] . For reasons that will be here discussed, fashion apparel consumption have been accused of being unsustainable and detrimental to the natural environment in the sense that entails renewable and nonrenewable natural resources depletion, emits dangerous substances into the air, water and land through toxic chemicals used in the production of fibres and textiles and creates unmanageable quantities of postconsumer solid waste sent to landfills [12,30]. This is because fast fashion apparel, often referred to as throwaway fashion, on one hand, is generally not designed to last long, and on the other hand, due to its lower prices and fast turnaround of fashion trends, encourages consumers to buy more than necessary and to dispose their clothes after only wearing for a few times [31,32] ultimately ending up in landfills instead of being recycled, re-used or re-purposed [33]. Paradoxically while consumers are becoming more environmentally and socially conscious, fast fashion has led to contradictory behaviour, because the literature shows that most consumers disregard sustainability when buying clothes [11,31]. In fact, studies show that consumers find it difficult to recognize sustainable brands and are often not willing to pay premium prices for green products or buy unfashionable apparel [11]. [34,35] Generation Y or Millennials, accounting for more than 25% of the world's population, are people born between 1980 and 1995-2000. They are characterized by being civic-minded, socially conscious individuals and consumers, searching for quality goods, willing to pay more for brand names and willing to pay extra for sustainable offerings [34]. The majority (77 %) claims to be concerned about the environment [24], for the fact that they were born during an era of environmental consciousness and active calls for action which, in turn, translates into a generation who is more apt to adopt pro-environmental behaviours [5]. Additionally, millennials are capable to influence their parents spending habits, which make them an attractive segment for marketers. However, the literature also shows that Gen-Y consumers exhibit disparities in their consumption behaviour making it difficult to marketers to comprehend their attitudes [27,37]. One important feature of Gen-y is that they tend to convey their identity through clothing and thrive to be seen as having different styles and appearances from their peers to show their uniqueness and self-image [27,35,36]. Reasons attached to self-esteem are also present in the literature, to justify millennials willingness to spend large amounts of money on clothing [27]. Hence, apparel retailers acknowledge the importance of researching their purchasing habits, but face challenges in trying to segment them accurately. Moreover, as the fashion market deals with changing consumer tastes and styles, understanding the basic psychology of apparel consumption became utterly important [27,37].

Conclusions
This study presented the results of a work-in-progress analysis and synthesis of the body of knowledge so far produced about green/sustainable consumption among Gen-Y consumers. Based on the systematic literature review methodology, the purpose was to uncover areas of inquiry that may help marketers to be innovative to attractive this segment of consumers, already considered as the most influential consumer group in the world [5]. Our review shed some light on the complexity of understanding concepts that are intertwined, namely, sustainable/green consumer behaviour, and attitude-behaviour gap in green/sustainable consumer behaviour, fashion industry's impact on sustainability and Generation Y or Millennials' behaviour towards sustainable fashion consumption. The literature is unanimous on the need to engage in in-depth research about this particularly segment and acknowledges that few researchers have examined Gen Ys' attitudes and behavioural intentions toward green issues [27,34]  We conclude this paper by collating opportunities for future inquiry in three different clusters. Firstly, this study provides clear features of Gen-Y consumers' purchase intention for green/sustainable fashion apparels, highlighting brand, style, price, and social identity as the most influential factors affecting their behaviour. However, knowledge should be deepened on how this segment develops their commitment towards pro-environmental purchasing behaviours and how their self-identity that is, their values, beliefs and education influence their interpretations of symbolic and functional attributes of the green/sustainable product or service [27,36]. Secondly, further research should investigate the effects of education on green/sustainable consumption and propose consumer educational programs that will encourage fashion consumers to change their behaviour toward reducing clothing consumption and waste production and to contribute to more sustainable practices integrated into their everyday lives [11,12,37]. Thirdly, in terms of implications for practitioners concerned with their green marketing strategies, this study unveils the need to stay connected with Gen-Y consumers using their own formats of communication, such as social media. As millennials are technology-oriented and highly exposed to social influence, tending to attach more importance to environmental messages that are communicated within their social networks [5], companies are advised to communicate their sustainability initiatives in posts, blogs, press releases to encourage consumers to choose sustainable apparel collections [18,24]. Moreover, as consumers claim to lack knowledge about companies offering sustainable apparel brands and state that they would like to learn more, marketing efforts, campaigns, and promotional activities should be placed on accurate communication messages promoting the benefits of green products and explaining the reasons why they are normally more expensive, due to its enhanced quality and limited availability when compared to non-sustainable products [18,24,37]. Hopefully this work-in-progress will stimulate future research on the topic, by integrating existing studies and providing a comprehensive set of compelling questions that needs further inquiry.