guest article by Sarah Köcher, finalist of the best dissertation Award 2019

Over the past two decades, rapid advances in technology and the omnipresence of the Internet have led to a fundamental change in our shopping behavior. While purchase behavior in traditional bricks-and-mortar stores is constricted by, for instance, limited retail spaces and finite opening hours, the Internet enables customers to shop anything, anytime, and anywhere. Moreover, while in the past, consumers were reliant on the quality of sales people’s advice or recommendations from their friends, they can now share their experiences and opinions about products, services, companies, and brands on a variety of websites with anyone. As a consequence, customers can easily access numerous online reviews at the click of a mouse. For example, TripAdvisor’s website offers more than 600 million reviews covering about 7.5 million accommodations, airlines, attractions, and restaurants, to 455 million unique users each month (TripAdvisor 2018).

As a young researcher and as someone who loves to shop online, several questions came to my mind as a customer; questions I wanted to answer as an academic. An abundance of research has shown that consumers’ inferences from online ratings are determined by average ratings (e.g., Chevalier and Mayzlin 2006; Dellarocas, Zhang, and Awad 2007; Godes and Mayzlin 2004), the number of ratings (e.g., Liu 2006; Moe and Trusov 2011; Zhu and Zhang 2010), as well as the dispersion in rating scores (e.g., He and Bond 2015; Sun 2012). Adding to this stream of literature, my studies demonstrate a tendency to use the mode – i.e., the most frequent rating a product has received – as a heuristic basis when drawing inferences from online rating distributions in such a way that product evaluations inferred from rating distributions with an equal average, standard deviation, and number of ratings systematically vary by the location of the mode. Thus, my work contributes to extant literature studying the impacts of product and service ratings in online shopping behavior. To collect the data for my studies I employed a variety of methods, ranging from experimental consumer studies, over an eye-tracking study, to secondary data from online platforms making it even more fun to conduct the research.

Furthermore, one of the key factors responsible for the enormous popularity of online reviews is that they are deemed highly credible and trustworthy (e.g., de Langhe, Fernbach, and Lichtenstein 2016; Jiménez and Mendoza 2013; Sen and Lerman 2007); despite the fact that they mostly stem from unknown strangers. Given that consumers heavily rely on online ratings – and honestly, this has been true for me as well – I was curious to learn whether such ratings can actually reflect the true quality of a product or a service: Surprisingly, I found that they do much less than one would expect.

As an academic, you always aim at publishing your research in high-quality journals. Thus, I was very delighted that one of my doctoral dissertation papers[1] was already published while finishing my PhD. Additionally, I found it rewarding to see that also the public was interested in my work and that it was also relevant to people outside academia in particular with respect to consumer protection. I felt honored that the media[2] reported about my doctoral work in (online) newspapers and that I was invited to talk about our research in TV and radio shows[3]. Finally, one of the best things was to have the opportunity to present my work around the world, to meet inspiring scholars and to start new projects aside from my doctoral research. I am very thankful for all the support I have received from my supervisors, colleagues, friends, and family and am very excited to continue my journey as an academic. I believe the most important thing – not only in academic life – is to be curious and passionate about what you do and to make an impact on people’s lives. This is why in particular service research caught my attention and I am grateful to be able to work in this fascinating field of research.

Dr. Sarah Köcher
Postdoctoral Researcher at the Department of Marketing, TU Dortmund University, Germany


[1] Köcher, Sarah and Sören Köcher (2018), “Should We Reach for the Stars? Examining the Convergence between Online Product Ratings and Objective Product Quality and Their Impacts on Sales Performance,” Journal of Marketing Behavior, 3 (2), 167-183.

[1] e.g.:,

[1] e.g.:


Photo: Image by Gerd Altmann from Pixabay


Chevalier, Judith A., and Dina Mayzlin (2006), “The Effect of Word of Mouth on Sales: Online Book Reviews,” Journal of Marketing Research, 43 (August), 345–359.

De Langhe, Bart, Philip M. Fernbach, and Donald R. Lichtenstein (2016), “Navigating by the Stars: Investigating the Actual and Perceived Validity of Online User Ratings,” Journal of Consumer Research, 42 (April), 817–833.

Dellarocas, Chrysanthos, Xiaoquan M. Zhang, and Neveen Awad (2007), “Exploring the Value of Online Product Reviews in Forecasting Sales: The Case of Motion Pictures,” Journal of Interactive Marketing, 21 (Fall), 23–45.

Godes, David, and Dana Mayzlin (2004), “Using Online Conversations to Study Word-of-Mouth Communication,” Marketing Science, 23 (November), 545–560.

He, Stephen X., and Samuel D. Bond (2015), “Why is the Crowd Divided? Attribution for Dispersion in Online Word of Mouth,” Journal of Consumer Research, 41 (April), 1509–1527.

Jiménez, Fernando R., and Norma A. Mendoza (2013), “Too Popular to Ignore: The Influence of Online Reviews on Purchase Intentions of Search and Experience Products,” Journal of Interactive Marketing, 27 (August), 226–235.

Liu, Yong (2006), “Word of Mouth for Movies: Its Dynamics and Impact on Box Office Revenue,” Journal of Marketing, 70 (July), 74–89.

Moe, Wendy W., and Michael Trusov (2011), “The Value of Social Dynamics in Online Product Ratings Forums,” Journal of Marketing Research, 48 (June), 444–456.

Sen, Shahana, and Dawn Lerman (2007), “Why Are You Telling Me This? An Examination into Negative Consumer Reviews on the Web,” Journal of Interactive Marketing, 21 (Fall), 76–94.

Sun, Monic (2012), “How Does the Variance of Product Ratings Matter?” Management Science, 58 (April), 696–707.

TripAdvisor (2018), “About TripAdvisor” (accessed April 17, 2018), [available at].

Zhu, Feng, and Xiaoquan Zhang (2010), “Impact of Online Consumer Reviews on Sales: The Moderating Role of Product and Consumer Characteristics,” Journal of Marketing, 74 (March), 133–148.

Doctoral dissertation:

Köcher, Sarah (2018), Reaching for the Stars: Consumers’ Interpretations of Online Rating Distributions and their Validity as an Indicator of Product Quality (