External evaluations under quality uncertainty: the market for wine ratings

Magalie Dubois¹, Jean-Marie Cardebat², Nikolaos Georgantzis¹

¹ School of Wine & Spirits Business, Université Bourgogne Europe, Burgundy School of Business, CEREN EA 7477, F-21000 Dijon, France

² Université de Bordeaux, INSEEC School of Business and Economics, France

*Corresponding author. Email: magalie.dubois@bsb-education.com

Abstract. The parallel development of scientific knowledge and technical practices over the last five decades has had a significant impact on sensory wine quality definition and evaluation. We conduct an integrative review of the literature on wine quality evaluation to determine the role of experts in the wine market, considering the recent changes. Following the updated methodology of integrative review proposed by Whittemore & Knafl (2005) [1], we conceptually structure the topic of quality evaluation and valuation in the wine market while critically analyzing the literature. The existence of a market for experts and aggregated peer evaluations is not fully explained by the profitability of the actors involved: wine media and online review aggregators. The residual value necessary for the subsistence of this market seems to be contributed by the wine industry. The present research demonstrates that professional wine evaluation does not meet the demand for quality evaluation and judgment delegation apart from fine wines. Subsequently, with the fall of the search cost for price, information, and expertise, we are witnessing a digital switch toward informal influence. This is to our knowledge the first integrative review spanning the emergence and development of the industry of information and specialized valuation in the major wine markets.

Keywords: information asymmetry, wine ratings, quality evaluation, prescription, digital transformation, online review aggregators, prosumers.

Index

1. Introduction

2. Literature analysis: Integrative review approach

2.1 Reasons behind the choice of an integrative literature review approach

2.2 Selection criteria

3. The market for quality evaluation

3.1 Analysis of the supply

3.1.1 Wine experts: only the best rated by only the best

3.1.2 Online review aggregators: all rated by all

3.2 Analysis of the demand

3.2.1 Wine consumers: lowering search costs effect

3.2.2 Fine wine investors and collectors: warranty effect

3.2.3 Wine producers and organizations: signaling quality as marketing strategy

3.2.4 Wine distributors and retailers: quality signaling as an intermediate product

4. Discussion

5. Conclusion

6. Limitations of the study and future research directions

Acknowledgements

References

Appendix

1. Introduction

The issue of uncertainty concerning a product’s quality represents a significant area of focus within the field of economics. In particular, the seminal work of Akerlof (1970) [2] and Spence (1973) [3] have highlighted the association between information asymmetry, a particular type of market inefficiency, and the necessity for quality signaling through product certification. Under information asymmetry, the advice provided to the less informed agents in the market becomes a valuable service for which a market may emerge. Contrary to the predicted consequences of informational asymmetries under quality uncertainty, the spontaneous emergence of an “intermediate market” for quality assessment by independent evaluators has received scant consideration. In fact, the theoretical foundations for the emergence of such a market without the need for a formal certification-conferring authority are anything but clear.

Compés-López et al. (2018) [4] suggest that an industry of information and specialized valuation has emerged in the major wine markets. Similarly, various papers refer to the existence or the emergence of a wine quality evaluation market, at the crossroads between wine sellers, wine buyers, and wine experts (e.g. [5],[6]). The present research proposes an integrative literature review of 267 papers (including publications from conference proceedings) on wine ratings, reviews and scores published from 1970 onwards retrieved from the Web of Science, Science Direct, Scopus, and Google Scholar databases. The objective of this integrative literature review is to collect and report some features identified so far in the literature, which should be considered in future theoretical and empirical analysis of such spontaneous intermediate quality evaluator markets. More specifically, it aims to provide a comprehensive overview of the existing research on wine ratings.

The review suggests the existence of an expanding two-sided market structure (this can be likened to the case of media, payments systems and matching markets) because the demand for expert opinion from wine consumers does not generate sufficient income to sustain the suppliers. Wine media must therefore subsidize readers (demand side one: customers) and make money out of advertisers or competition entry fees (demand side two: wine trade). Meanwhile, online review aggregators (platforms that gather user-generated reviews on different products into one easy-to-view dashboard, as is the case with Vivino) subsidize the free of charge (zero price) of online prosumer (in this case wine consumers who actively share their product experience participating in the production of wine reviews) reviews by charging commissions on sales (or by selling wine directly to their users) and selling both promotional services and data intelligence to the trade. Our integrative literature review highlights the fact that the survival of both experts and online review aggregators is dependent on the trade.

To the best of our knowledge, our paper represents a pioneering discussion of the complementarity of the two quality signal sources (experts and peers), each associated with a specific demand type. In this respect, it provides useful support for recent developments on (two-step) hedonic functions by type of actor [7]. At a more foundational level, our findings offer a promising avenue for exploring the potential implications of such an information market on the wine market, particularly in terms of marketing, operational and strategic management, and finance.

2. Literature analysis: Integrative review approach

2.1 Reasons behind the choice of an integrative literature review approach

In contrast to systematic literature reviews, integrative literature reviews are more flexible ways to synthesize existing research. It allows for a diverse range of sources, including theoretical, qualitative, and quantitative, to be incorporated in order to develop new frameworks, identify potential research gaps, and provide a comprehensive understanding of a given topic. Because research on wine evaluation is fragmented, originates from different fields (e.g. economics, marketing, sensory sciences, linguistics) and uses multiple study designs and methodologies (e.g. hedonic price function, experimental economics, content analysis, principal component analysis), the use of an integrative literature review is indicated [8]. Integrative literature review methodology proves particularly useful when studying a recent change in the direction of a phenomenon [8] such as the emergence of peer evaluation as the source of a potential paradigm shift in the wine evaluation market identified by Bazen et al. (2022) [9]. Unlike systematic reviews, integrative literature reviews are versatile, they allow the use of “grey literature” such as conference proceedings [10]. We acknowledge that those publications do not offer sufficient guarantees as validated knowledge, but we consider that the importance of the insight they provide in the study of a recent phenomenon is a sufficient justification for their careful consideration.

Following the integrative literature review methodology revised by Whittemore & Knafl (2005) [1], we structure the topic of quality evaluation and valuation in the wine market. A comprehensive literature search is conducted across multiple databases, including empirical studies (e.g. [11]), theoretical papers (e.g. [12]), and grey literature (e.g. [13]) using specific inclusion and exclusion criteria to ensure relevance. Subsequently, the quality and relevance of the selected studies are subjected to critical assessment using staged review. The data analysis phase entails the identification of themes and patterns through thematic analysis, with the findings subsequently organized into coherent themes. Ultimately, the review synthesizes the findings into a coherent narrative, highlighting research gaps.

2.2 Selection criteria

The vocabulary used to refer to quality evaluation, quality signaling and quality evaluation intermediaries in the wine market is extensive (see Table 1).

Considering this diversity, we have deliberately opted for broad inclusion criteria to capture the evaluative content produced by experts and peers. Using Boolean logic, the search strings in Web of Science, Science Direct, Scopus, and Google Scholar databases consisted of the terms wine ratings, wine review, and wine scores, including synonyms, and abbreviations. Recently published peer-reviewed articles and earlier literature (from 1970 onwards) published in English were searched. We also reviewed the articles citing the articles obtained through this search as well as their references to identify further potentially relevant studies. The record selection process is displayed in Figure 1.

A total of 530 books and papers published prior to July 2023 were identified and 83 duplicate records were removed prior to screening. Subsequently, the remaining records were screened on the basis of content, with 120 papers (in particular, those comparing the sensory performances of experts and consumers) being excluded. Ultimately, 267 papers were selected for the integrative review following detailed analysis using staged review. The number of records per year in the final selection appears in Figure 2.

Among the records selected for the integrative review, the Journal of Wine Economics, first published in 2006, is by far the best represented (59), followed by the International Journal of Wine Business Research (16), the Journal of Wine Research (18), and Food Quality and Preference (13). The overview of all final used papers within the scope of the integrative literature review is available in the Appendix.

The analysis of the literature is facilitated by the deconstruction of the topic into the key relationships and interactions between the supply and demand sides of wine quality information.

3. The market for quality evaluation

3.1 Analysis of the supply

3.1.1 Wine experts: only the best rated by only the best

Definition

Professional wine experts possess both conceptual knowledge (of terroirs, grape varieties, vintages) and perceptual (sensory) knowledge of wine [31],[32]. While opinion leaders are traditionally difficult to identify, since the 1970s professional wine expert tasters have identified themselves through their public roles [33]. According to Fernandez (2004) [34], in the wine market, the core of wine critics’ activity remains the publication of wine reviews and consumer guides: their opinion is their living. The most influential publications in this field include Decanter, The Wine Spectator, the Wine Advocate and a number of prominent individual critics, such as James Suckling, Jancis Robinson and Tim Atkin. Figure 3 presents the main interactions between wine experts and the stakeholders of the primary market.

Rated wines

Given the constraints on the number of bottles that they are able to taste and evaluate on an annual basis, experts tend to prioritise their prescription work on fine wines, which are characterised by higher prices and superior reputations1. The Wine Spectator tasting team reviews more than 15,000 wines a year, they also exclude thousands of (often non-premium) wines from their selection [35]. The majority of these businesses have come to rely on solicited samples to maintain a sustainable equilibrium within their business models. The reliance on solicited samples might explain the censorship applied to negative reviews by wine experts [36]. A negative rating on one vintage could jeopardize the possibility of receiving samples the following year [34],[37],[38]).

Top critic scores are crucial globally for en primeur [14],[39], however, it is a common practice amongst producers of super-premium wines to decline participation in blind reviews; the potential for an unfavourable assessment to generate adverse publicity is a significant concern in this regard. Nevertheless, quality ratings hold little significance beyond the domain of fine wines [40–42].

Audience

The market structure for experts is complex due to the diversity of their publishing channels2: they can own publications, wine magazines, specialized and general print press, and online channels [43–44]. According to Storchmann, discussing the US wine market fifteen years ago (2012, p. 22 [45]), “The market for expert opinion on wine is large. The seven major U.S. wine magazines have a combined subscribership of more than 500,000, with 350,000 alone for the Wine Spectator; wine magazine sales total more than $25 million”. Today, most of the wine publications mentioned by Storchmann in 2012 (data from 2010) have increased their readership base. The three major U.S wine magazines (Wine Spectator, Wine Enthusiast, and Wine & Spirits) have a combined subscribership of more than 750,000, with 389,000 alone for the Wine Spectator [46]. Online marketplaces also supply wine critics (especially English-speaking ones) with a much wider network of prescriptive channels and reach than ever before [47–48].

Still, researchers deplore the difficulty of determining the area of influence beyond publications and subscribers, as well as the scarce availability of figures on publications and sales of magazines and guides dedicated to wine [49]. We know that wineries are important customers for guidebooks, as they tend to share them among themselves [50]. However, there is no mention made in the literature of the proportion of this subscription or of the purchase of guides actually generated by the trade (e.g., wine producers, distributors, retailers) and not by wine consumers3. Likewise, the subscriptions figures do not reveal possible overlap (especially among professionals) nor the indirect reach of experts (e.g., one magazine can be read by multiple readers, word of mouth).

Business model

The main source of revenue for wine critics and magazines is circulation and advertising revenue as well as subscriptions to access their ratings: their value for advertising increases with the number of readers. When critic’s ratings are not displayed in store or online at zero price, wine consumers are usually charged with positive prices (subscription) to access them.

Criticisms

Wine experts have been found to be less reliable and consistent than experts in fields such as medicine, clinical psychology, business, auditing, personnel management, or meteorology [51]. They have even been charged with opportunistic behavior, grade (rating) inflation, and conflict of interest [22]. The accuracy of wine experts’ judgment has been challenged, particularly by Ashenfelter & Jones (2013, p. 1[52]): “the expert opinions are not efficient, in the sense that they can be easily improved, and that these opinions must be demanded, at least in part, for some purpose other than their accuracy”. In his study of publication bias in Wine Spectator, Reuter (2009) [53] suggests that wine consumers may be more tolerant of review bias than consumers of other product categories, due mainly to the subjectivity of wine tasting

The business model of experts is based on two main revenue streams: subscriptions and the sale of advertising space. Although there is no evidence to suggest that advertising spending directly impacts wine scores, it can be posited that companies which invest in advertising within wine publications are more likely to be chosen by wine critics to have their wines tasted. The wine magazines could be suspected of opportunistic behavior to attract more advertisers (wine sellers). However, Reuter (2009) [53] studying Wine Spectator publication bias (product coverage and review) concluded that advertising influences ratings only on the margin, particularly enhancing retasting of wines rated less than 70 during the first single-blind tasting. According to him, wine media’s readership is a function of both subscription prices and the publication’s reputation for being unbiased [53].

Experts rate, usually blind tasting, both the present and future value of wine, while peers rate it, usually not blind, only through the scope of their current appreciation [54]. This leads Schiefer & Fischer (2008) [55] to question the usefulness of wine experts’ ratings as a predictor of wine consumer liking and to infer that most expert ratings do not reflect consumer taste. Even though the prior knowledge of price, brand and reputation may bias their appreciation [56] peers may be more relevant than experts to super-premium available wines for example, because they may taste them more often than critics. More bankers than wine critics can afford drinking/tasting Domaine de la Romanée Conti.

Future perspectives

The evolution of other experience goods markets, such as art or hospitality, foresees the disappearance of experts in favor of peer recommendations [57–58]. Cox & Kaimann (2015) [59] predict that the growing influence of word-of-mouth and consumer-generated content in consumer purchase decision-making could decrease consumers’ reliance on the opinions of experts or professional critics. Clauzel et al. (2019) [60] recommend that experts capitalize on the empowerment of consumers by integrating prosumers’ reviews into their content, alongside their own ratings. A similar trend (see Figure 4) might be ongoing in the wine industry [61–62].

3.1.2 Online review aggregators: all rated by all

Definition

A participatory culture is emerging among consumers [63]. Unofficial and informal prescription is gaining importance in the wine market; consumers’ tastes (general hedonic rating) prevail over quality evaluation because the personal taste is simply more relevant than quality when choosing a wine [55]. Experts are no longer the only benchmark for quality, the wisdom of the crowd is gaining prevalence for knowledge construction and evaluation [57]. With the internet and the emergence of online ratings, wine consumers have shifted from passive to active purchase evaluation, and their comments displayed online provide an informative signal of quality [64]. “That is democracy at an organoleptic level; it is subjective individualism raised to a moral principle.” (Shapin, 2012, p. 83 [65]). The wine drinkers who share their wine-tasting experience on platforms like Vivino, CellarTracker or Delectable also produce information about wine quality. Online review aggregators bundle this (prosumers) user-generated content (UGC) to provide quality information to other users, creating what Chan et al. (2022) [66] call “prosumers communities”.

Rated wines

The remarkable sales figures of The Wine Trials [67] indicated a potential demand for more consistent evaluation of everyday wines. Prosumer communities cover all wine categories without discrimination4. Online review aggregators have expanded the market for wine quality evaluation, providing ratings where they were not available before (cheaper wines) and supplying those ratings aggregated at zero price (free of charge).

Audience

The world’s largest online wine rating community and marketplace, Vivino, claims no less than 29.9 million users and 89.4 million ratings. The first academic mention of Vivino in a working paper dates back to 2018 [68]. The evolution of the number of users, wines, wineries, scanned labels, and ratings since 2014 is detailed in Table 2.

Vivino’s wide adoption has been facilitated by the rise of apps use from more than 2.7 billion users [69]. Comparatively, CellarTracker, another online review aggregator and inventory management tool5 mostly used by wine collectors, claims 4.3 million wines and 11.8 million community and professional ratings (compared to 7 million in the summer of 2018).6 Its users (232,000 in 20127) manage more than 164 million bottles in their private cellars and have access to professional experts’ ratings, market value, and inventory management [70–71].

Business model

The business model of online review aggregators revolves around user-generated content, monetized through advertising, premium subscriptions, affiliate marketing, and data analytics. These platforms provide a space for users to review, rate, and discover wines while offering targeted advertising opportunities for wineries and retailers. Premium subscriptions unlock advanced features like cellar management tools, expert recommendations, or exclusive content. Revenue is also generated through affiliate partnerships, directing users to purchase options and earning commissions, as well as by licensing anonymized consumer data to industry stakeholders for market insights.

Criticisms

Online review aggregators declare tackling the negative review censorship issue8. However, they fail to mention three major issues with community ratings. First, the under-reporting bias [72]: prosumers might not be willing to spend (waste) time scanning, rating, or reviewing the wines that they dislike. Under-reporting leads consumers to comment only on the wines they liked or disliked a lot. Second, the acquisition bias [73]: a positive predisposition towards a wine enhances purchase and comment generation likelihood. Ultimately, beyond these two forms of self-selection bias remain the considerable variations in wine knowledge levels of the users, along with the significant problem of fake reviews [74].

Future perspectives

The limitation of expert wine evaluation to fine wine and the complexity of the evocative vocabulary have created an opportunity for peer-reviewing [75]. The importance of crowdsourcing prosumers’ opinions is increasing, and so is their impact on the market [36],[76]. More specifically, hedonic price function estimates suggest that wine prices are better explained by online community rating scores than by expert ratings [20],[77].

To sum up, there are two sources of quality ratings in the wine market, offering heterogeneous information products (experts versus community ratings) at different prices (positive versus zero-price i.e. free of charge). Historically dominated by wine experts (reviewing only fine wines), evaluative intermediation now reaches cheaper wines and a wider audience with online review aggregators (see Table 3). This has the effect of complicating the determination of whether they may be considered substitutes or complements.

3.2 Analysis of the demand

3.2.1 Wine consumers: lowering search costs effect

Most consumers declare that liking a specific wine they tasted before is the most important reason for their (re)purchase [78],[79]. However, previously purchased wines are not systematically available for purchase (see on-trade for example). Since wine is an experience good, wine quality evaluation only occurs through post-purchase consumption. Wine consumers are subject to information asymmetry. Moreover, unlike in other markets (education, finance), the wine market offers no homogenized institutional quality signaling system at a global level [80]. The high complexity and heterogeneity of existing quality signaling systems (e.g. Geographical Indications in the European Union and the United States) can be perceived as confusing by consumers, who may look for alternative sources of quality information [81–83]. More broadly, the complexity of the wine market is a source of consumer confusion and qualifies wine buying as a risky activity for most wine consumers [84].

When confronted with uncertainty about product quality, consumers often use multiple product quality cues as proxies for quality [85],[86]. Another solution to cope with this confusion is for consumers to rely on better-informed agents when making their decisions [87]. These third parties supply homogenous information mapped on a single rating scale comparable among wines [62]. To reduce perceived risks when selecting a wine and to maximize their satisfaction, wine consumers can delegate quality judgment to others [29]. They seek the advice of wine experts, friends, family members, and clerks who are deemed knowledgeable [88]. There is a wide literature on wine experts focused on perceived risk reduction and subsequent purchase intention stimulation [89],[90],[91]. Although experiential information has the highest informational content, sources of quality evaluation such as peers have not been extensively investigated [92].

3.2.2 Fine wine investors and collectors: warranty effect

The classification presented here is the result of a balanced structure within the paper itself, rather than the result of the preferences of fine wine investors and collectors being homogeneous. However, Masset (2024) [93] suggests that the preferences of investors and collectors are equally influenced by the reputation of wines. Since professional wine experts work as proxies for rating agencies, wine critics’ scores have opened the market for Bordeaux fine wines to investors [94]. The financial indices of Liv-ex.com were built using wines rated 95 and above by Robert Parker [95]. Liv-Ex is nowadays the primary electronic exchange platform for trading fine wine. Merchants, brokers, retailers, and consumers can use the platform to purchase these wine futures in advance of their distribution for retail operations. Along with the process of financialization in the fine wine market, several economic studies have shown the correlation between experts’ ratings, en primeur, and auction prices (e.g. [11],[22],[96]). Wine is the only agricultural market to have reached such a valorization of variability in the premium part of its market [97]. But there might be an interdependency here since in her attempt to identify the macroeconomic determinants of fine wine prices, Jiao (2017) [98] concluded that the increasing volatility of prices triggers demand for expert appraisal from fine wine investors. The influence of expert information on price is subject to variation over time. In a hedonic analysis of fine wines, Faye & Fur (2019) [99] demonstrated that, in contrast to the Parker score, the Quarin (French critic) score exerts a remarkably stable influence on price. Similarly, it may be posited that the influence of peers on valuation is likely to be contingent on price levels [100].

3.2.3 Wine producers and organizations: signaling quality as marketing strategy

The determination of wine prices is no longer solely contingent upon production costs. Instead, they are also influenced by the collective reputation of the region or geographical indication, as well as the individual reputation of the brand [49],[101],[102],[103],[104]. The marketing of quality, a key element of a differentiation strategy for wine producers, involves close contact with critics as part of their communication and reputational strategy [105]. Evidence abounds that reviews of professional critics enhance commercial success, though consumer sensitivity to reputation is higher for premium, super-premium, and icon wines [59],[106]. Wine reputation is positively correlated with expert ratings [20]. Collective reputation is shown to have an impact on consumers’ willingness to pay, which rises in line with the reputation of individual wine producers [102]. The individual reputation of wineries will also enable them to select their retailers and distributors depending on the positioning they wish to reflect: hotels, restaurants, independent wine stores and export for fine wines, and supermarkets for bigger-volume wine producers [107]. This explains why, for high-end wineries, reputation management can become almost as important as revenue management [108]. Organizational reputation has become a strategic intangible asset for firms and is one of the most important drivers of their success [109], which is why some companies place wine critics at the core of their marketing and communication strategy [110].

Wine critics benefit from close contact with wine producers enabling them to publish interesting articles and well-informed reviews. They reciprocate by disseminating products and company messages [111]. “Producers, and intermediaries such as distributors and retailers, often use favorable reviews to promote products, resulting in a multiplier effect for evaluation where the eventual audience can be far broader than the direct audience (e.g., paid subscription).” (Kwon & Easton, 2010, p. 136 [95]).

3.2.4 Wine distributors and retailers: quality signaling as an intermediate product

The academic literature has studied the effect of shelf-talkers (product cards including ratings that appeal in stores) on sales, and shown from early on their positive correlation with sales: scored wines outsell non-scored wines in retail studies (e.g. [112],[113]. Retailers are therefore encouraged to use a wide range of wine experts’ references in shelf talkers that will boost their sales. Distribution networks are increasingly important in the wine evaluation market, reflecting the transformation of economic competition into a more vigorous struggle for attention and visibility [50],[95],[114]. Hsu et al. (2012) [115] and Hennion (2015) [116] underline the importance of evaluative schemata (mental representations of evaluative categories) and procedure clarity, to help both consumers and producers cope with uncertainty, and to allow producers to anticipate quality assessment and adequately adjust their production strategy. Even when distributors, retailers, or sommeliers state that they do not pay attention to ratings, their audience base (customers) might force them to recognize the judgment of critics and to adapt to it, listing iconic 100-point wines, for example [117]. Bazen et al. (2023) [77] additionally highlighted the increasing significance of Vivino ratings for wine importers.

4. Discussion

Even though the empowerment of the vox populi in the wine market has been noticed for almost two decades, the existing literature about online consumer-generated content on wine remains scarce outside of the context of wine tourism [118]. In a recent European survey, more than 30% of the 7,324 respondents stated that they had a wine app on their mobile phone9 [119]. Nevertheless, only a limited number of papers have integrated prosumers’ reviews in their reflection (e.g. [62]) or compared their relative influence with experts’ ratings using empirical (e.g. [20],[77]) or experimental methods [19],[21],[120]. Still, part of the literature available on the topic consists of working papers, unpublished in peer-reviewed journals to date [20–21,56,121–123], In 2022 only, more than 10 projects using Vivino data were presented at the three major wine economics and business conferences in 2022 (European Association of Wine Economists, American Association of Wine Economists, Academy of Wine Business Research). The most recent publication available investigates the emotional response to Vivino reviews exposure [124]. As there are to date no published studies that used other methods than hedonic price analysis to compare the influence of peers’ and experts’ ratings in the wine market. The results reported here should be considered as part of a larger effort to develop more empirical research about the wine evaluation market.

Analyzing both sides of the market, this review highlighted the financial reliance of wine experts and online review aggregators on the wine trade. Both expert and consumer assessments of quality are similarly uncertain and susceptible to various biases. This may provide an explanation for the reluctance of consumers to pay a premium for these services. This review highlighted the fact that only a tiny proportion of the ratings users are willing to pay for a subscription to get access to wine evaluations. While the majority of consumers do not disregard the value of ratings when obtained for free, they are not willing to pay for it10 [80]. This is why a vast majority of experts rely on free requested samples and advertisement income to carry out their activities. Without the sale of advertisements (and more recently other side activities like competition or events), most wine publications would not be profitable [53]. Nor would the online review aggregators without the sale of wine promotional services and data [126]. The present integrative literature review reveals that both revenue models are based on two-sided strategies (See Figure 5).

According to Evans (2003) [127] in two-sided markets, the intermediaries must (1) select a price and (2) use a differential pricing structure (not only how much they will charge, but to whom). They usually skew the prices on the less price-sensitive side of their two sets of customers. The wine valuation market behaves like a two-sided market when suppliers subsidize one side of the market to earn profit from the other side.

Experts’ ratings reach three different categories of stakeholders: industry readers, consumer readers and consumers who see scores in the store or online (not to mention word of mouth from any of those three categories of stakeholders). Wine consumers, investors, and collectors can pay to get access to most of the media through which expert reviews are conveyed: Magazines, guides, and online reviews. But information is also made available at zero price (often in exchange for viewing advertisements on the platforms) to consumers: wine ratings and awards are frequently displayed in both online and brick-and-mortar shops.

Meanwhile, online review aggregators provide free ratings to their users. Those free ratings inform the customers of their marketplace, which positively impacts sales (including commissions or sales margin). Wine producers, distributors, and retailers do not pay to have their wines listed by online review aggregators. Prosumers review wines for free through their smartphones or computers. But producers must pay if they want to correct inaccuracies in the information available about their wines on the platform, advertise their production (enhancing their profile or purchasing triggered email campaigns), or purchase data about specific markets and consumers’ preferences (brand awareness, engagement, sales)11. Wine producers, distributors, and retailers also pay fees to list their wines in competitions (and potentially receive an award), and to advertise in the wine media. Based on the review of the literature, Table 4 presents the two-sided strategies for experts and online review aggregators.

Online review aggregators in the wine market benefit from both positive same-side and cross-side network effects. The increasing number of Vivino users, for example, feeds the platform and increases its utility to other users (same side). At the same time its value as a data provider or as a marketplace for wines increases with the number of potential customers (cross-side). It is possible for new players to enter the evaluation market at a limited cost; however, new online review aggregators will suffer from a competitive disadvantage, as the utility they offer both their users and potential customers of data or marketplace solutions depends on their number of users. Conversely, the path to success for new experts lies in building awareness and establishing credibility which typically takes time,

5. Conclusion

Two sources of wine ratings coexist on the market: experts and online review aggregators. While the literature on wine experts is extensive, the one on online review aggregators remains scarce. The supply of professional quality evaluation (wine experts) is characterized by its multiplicity and fragmentation over the years whereas online review aggregators offering for-free content are highly concentrated in the market, corroborating the conclusions of Barnett (2018) [128]. In other experience goods markets, such as hospitality, the influence of peer ratings now surpasses the influence of experts’ ratings. In the wine market, their coexistence illustrates two different definitions of quality. Professional wine experts focus on fine wines, charge positive prices to access their ratings (subscription) and impact the entire value chain (production, sales, consumption). In the meantime, peers rate all kinds of wines, for free, across a wider price range. While the Wine Spectator experts claim to produce 15,000 wine ratings a year, the Vivino community produces more than 31 million12. While the Wine Advocate prides itself on the 450,000 ratings housed in their online database, Vivino has 620 times more. If online review aggregators become the dominant evaluation source on the market, they could similarly influence the market and different wines could be favored. Since they rate all wine segments, it may lead to a renewal of the demand for less high-end wines globally.

This integrative literature review of the recent trends underlying the market for wine quality evaluation reveals various interesting patterns. Even though the importance of experts is decreasing, the wine market is likely to sustain both peer and expert quality information sources in the long run (they complement rather than substitute for each other). Their coexistence is likely to sustain and stimulate the E-commerce market for wines in the coming years, including direct-to-consumer (DTC) sales. The literature review has revealed that both sources of ratings base their business models on a two-sided strategy and could not be sustainable without the trade. Online review aggregators offer free access to wine drinkers’ reviews and use the generated data to source and sell popular and high-rated wines to their users. In the meanwhile, they also act as marketplaces, collect sales commissions, and sell promotional services as well as data intelligence to the industry. Based on this review we do not foresee a disappearance but a decline of wine experts (in the limited perimeter of fine wines), and a rise of the importance of online review aggregators in the wine evaluation market globally. Pure content producers such as The Wine Advocate, who employ one-sided structures (subscriptions are their only source of revenue), are likely to remain small13 and be disfavored by competition against online review aggregators as their consumer base grows older. The predictions identified by this literature review are in line with the conclusions of Kwon & Easton (2010) [95] and suggest that the future lies in hybrid internet-based evaluation aggregators, like Vivino, that combine the functions of review aggregator and marketplace.

This review has important implications for managers. With the expansion of the audience of online review aggregators emerges the possibility that the so-called “wisdom of the crowd” (or “preference of the crowd” [62]) channels attention to a limited number of products already favored by other consumers. The importance of a plurality of supply of wine evaluations is therefore of prime importance for the sustainability of the wine market: online review aggregators inform customers, complementing the work of wine experts that attract attention to producers. Online review aggregators contribute to the stabilization of a hierarchy in which professional experts sustain the variability of an artistic fine wine market where no two wines should be perfectly identical, even to two vintages of the same wine (see [97]).

6. Limitations of the study and future research directions

This study has integrated fragmented literature in the domain of wine quality information intermediation following the integrative literature review methodology revised by Whittemore & Knafl (2005) [1]. We acknowledge that combining diverse data sources and methodologies can be challenging. Despite the adoption of an exhaustive data collection strategy, the selection of inclusion criteria might have led to the omission of parts of the literature. For example, the Journal of Wine Economics, the leading outlet of articles related to the scope of the thesis, did not require keywords until 2013, which may have resulted in some missing references. An investigation into the ripple effects that the wine evaluation has on the wine market would have provided valuable insight. However, such an estimate is complicated by the opacity of the transactions (e.g., advertisements, price of promotional services or data intelligence) between stakeholders in the market. Seemingly, the value generated by the wine evaluation market cannot be easily measured through price. In the light of our findings, it would also be interesting to tackle the question of the long-term viability of expert ratings in the wine industry.

The disappearance of the border between the marketplace and prescription is also a central question for the wine industry. The acquisition of prosumer data gives online review aggregators access to valuable knowledge about consumer preferences that may provide them a competitive advantage over traditional competitors (experts). Online review aggregators can, as Vivino does, purchase and sell themselves the wines they have identified as being the most popular or the wines with highest potential according to their users and earn a direct sales margin instead of a commission on sales. Artificial intelligence is set to enhance the worth of this category of data, enabling a more precise targeting of consumers and sales of wine. Similarly, finding out how online review aggregators may affect wine producers’ marketing strategies would be of utmost interest to the industry.

When wine experts supply information on wine quality, online review aggregators also provide their users with a personalized likelihood of liking based on past evaluations. The consumer purchasing path has been fundamentally transformed by recommendation systems, offering customized choices while obviating the requirement for intensive information search [129]. The rating of a wine does not tell you how it tastes, nor if you will like it. How do consumer past evaluations influence their likelihood to adhere to personalized recommendations generated by algorithms? The exploitation of consumer data by wine sellers (sourced from online review aggregators) to mitigate the information asymmetry prevalent in the wine market (by gaining insight into consumer preferences) is likely to emerge as a key research area in the near future.

Acknowledgements

The authors deeply appreciate the insightful comments provided by Larry Lockshin, Günter Schamel, Robin Goldstein, and Lara Agnoli. Their constructive feedback significantly contributed to the development of this work. We also extend our sincere gratitude to the anonymous reviewers, whose thorough and critical assessment was invaluable in substantially improving the quality of this manuscript.

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Appendix

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