Topics: ICT Search and Innovation, Firm Behavior; Content Networks and Social Media.
“When Private Information Settles the Bill: Money and Privacy in Google’s Market for Smartphone Applications”, with Patrick Schulte (ZEW), 2017 (R\&R at Management Science, available as ZEW Discussion Paper 14-131., 2014 abstract cf. below)
“IT Outsourcing and Firm Productivity: Eliminating Bias from Selective Missingness in the Dependent Variable,” with C. Breunig (HU Berlin), J. Ohnemus (ZEW, Mannheim) and S. Viete (ZEW, Mannheim), 2017 (under submission; available as ZEW Discussion Paper No. 16-092)
-“Attention in the Peer Production of User Generated Content,” 2017“Economic Downturn and Volunteering: Do Economic Crises Affect Content Generation on Wikipedia?” with Olga Slivko (ZEW) and Michael X. Zhang (HKUST), 2017 (available as ZEW Discussion Paper No. 15-078)
“Wikipedia matters.”, with M. Hinnosaar (C. Carlo Alberto), T. Hinnosaar (C. Carlo Alberto) and O. Slivko (ZEW, Mannheim), 2017, available here
Work in Progress:
“User Data, Market Power and Innovation in Online Markets – Evidence from the Mobile App Industry,” with Patrick Schulte (ZEW, Mannheim) und Reinhold Kesler (ZEW, Mannheim), 2017 (nominated for DRUID Best Paper Award)
“Mobile Applications and Access to Private Data – The Supply Side of the Android Ecosystem,” with Patrick Schulte (ZEW, Mannheim) und Reinhold Kesler (ZEW, Mannheim), 2017
“Healthy Ecosystems for Online Reviews,” with Uli Laitenberger (Paris Tech) and Erin Strumpf (McGill)
“Geographical Price Discrimination in Online Markets – Evidence from Russia (with O. Slivko and I Yamtchikov, 2013)”
“Customer Reviews as Public Information Good in Online Markets” (with F. Hackl), 2010
“Market Entry in E-Commerce” NET Institute Working Paper No. 08-23, with Maximilian Kasy (U. Harvard), 2008
Refereed Journal Publications:
Hackl, Franz, Michael Kummer, Rudolf Winter-Ebmer and Christine Zulehner (2014), Market Structure and Market Performance in E-Commerce, European Economic Review68, 199 – 218. [download]
Refereed Conference Publications:
Giorgidze, George , Torsten Grust, Iassen Halatchliyski and Michael Kummer (2013), Analysing the entire Wikipedia history with Database Supported Haskell, in: Kostis Sagonas, Practical Aspects of Declarative Languages, 15th International Symposium, PADL 2013, Rome, Italy, January 21-22, 2013, Proceedings Series: Lecture Notes in Computer Science Bd. Vol. 7752, Rome, Italy. [download]
What can additional attention contribute to the high quality and quantity on user generated content networks? Correlations abound in such networks, but it is typically difficult to identify causal effects or merely exogenous sources of variation. This paper proposes to use observable (ex-post) local shocks in attention, such as natural disasters, to analyze how attention contributes to content generation. I analyze the effect of more than 90 pseudo-experimental shocks to attention on content contributions to articles that are linked to shocked articles. I find that 1000 aggregate views generate 1 edit. The target article’s characteristics, such as length, do not influence initial attention, but matter for the conversion of attention to subsequent contributions. However, attention driven contributions seem to add only marginally to already well developed articles, but they do not lead to substantial content additions on short articles.
“When Private Information Settles the Bill: Money and Privacy in Google ˇApps Market for Smartphone Applications”,
We shed light on a money-for-privacy trade-off in the market for smartphone applications (”apps”). Developers offer their apps cheaper in return for greater access to personal information, and consumers choose between lower prices and more privacy. We provide evidence for this pattern using data on 300,000 mobile applications which were obtained from the Android Market in 2012 and 2014. We augmented these data with information from Alexa.com and Amazon Mechanical Turk. Our findings show that both the market’s supply and the demand side consider an app’s ability to collect private information, measured by their use of privacy-sensitive permissions: (1) cheaper apps use more privacy-sensitive permissions; (2) installation numbers are lower for apps with sensitive permissions; (3) circumstantial factors, such as the reputation of app developers, mitigate the strength of this relationship. Our results emerge consistently across several robustness checks, including the use of panel data analysis, the use of selected matched ”twin”-pairs of apps and the use of various alternative measures of privacy-sensitiveness.
When contributing content to large and highly structured online platforms like Wikipedia, producers of user-generated content have to decide where to contribute. This decision is expected to depend on the way the content is organized. We analyse whether the hyperlinks on Wikipedia channel the attention of producers towards more central articles. We observe a sample 7, 635 articles belonging to the category economics on the German Wikipedia over 153 weeks and we measure their centrality both within this category and in the network of over one million German Wikipedia articles. Our analysis reveals that an additional link from the observed category is associated with around 140 bytes of additional content and with an increase in the number of authors by 0.5. The relation of links from outside the category to content creation is much weaker. Download
An earlier version was circulated as, “Centrality and Content Creation in Networks – The Case of German Wikipedia“, ZEW Discussion Paper No. 12-053, Mannheim.
Networks are widely believed to generate important spillovers and peer effects. However, quantifying such externalities has traditionally been challenging, because networks often form endogenously. This problem can be circumvented if one can find or create exogenous changes in a network structure. I find such exogeneous variation in the setting of German Wikipedia. Wikipedia prominently advertises a featured article on its main site every day. The added exposure exogeneously increases viewership of this article, while shifts in the viewership of adjacent articles are likely due to their link from the treated article. Through this approach I isolate how the link network causally influences users’ search and contribution behavior. I estimate how attention spills to neighbors through these transient shock in a difference-in-differences analysis. I further develop an extended peer effects model which relaxes the requirement of exogenously given networks to allow estimating the underlying spillover. Advertisements affect neighbors substantially: They increase views on neighbors by almost 70 percent. This, in turn, translates into increased editing activity. My methods apply even if identification through partial overlaps in the network structure fails.An earlier version was circulated as “Spillovers in Networks of User Generated Content – Evidence from 23 Natural Experiments on Wikipedia” and is available as ZEW Disc. Paper 13-098.