Spillovers in networks of user generated content : evidence from 23 natural experiments on Wikipedia

Endogeneity in network formation hinders the identification of the role that social networks play in generating spillovers, peer effects and other externalities. This paper tackles this problem and investigates how the link network between articles on the German Wikipedia influences the attention and content generation individual articles receive. Identification exploits local exogenous shocks on a small number of nodes in the network. It can thus avoid the usually required, but strong, assumptions of exogenous observed characteristics and link structure in networks. Exogenous variation is generated by natural and technical disasters or by articles being featured on the German Wikipedia’s start page. The effects on neighboring pages are substantial; I observe an increase of almost 100 percent in terms of both views and content generation. The aggregate effect over all neighbors is also large: I find that a view on a treated article converts one for one into a view on a neighboring article. However, the resulting content generation is small in absolute terms. My approach also applies if, due to a lack of network data, identification through partial overlaps in the network structure fails (e.g. in classrooms). It helps bridge the gap between the experimental and social network literatures on peer effects

99 cent: Price points in e-commerce

Basu (2006) argues that the prevalence of 99 cent prices in shops can be explained with rational consumers who disregard the rightmost digits of the price. This bounded rational behaviour leads to a Bertrand equilibrium with positive markups. We use data from an Austrian price comparison site and find results highly compatible with Basu's theory. We can show that price points - in particular prices ending in 9 - are prevalent and have significant impact on consumer demand. Moreover, these price points are sticky; neither the price-setter itself wants to change them neither the rivals do underbid these prices, if they represent the cheapest price on the market. --Competitive Behaviour,Pricing Behaviour,E-Commerce,Pricing in the Nines,Focal Pricing

99 cent: Price Points in E-Commerce

Basu (2006) argues that the prevalence of 99 cent prices in shops can be explained with rational consumers who disregard the rightmost digits of the price. This bounded rational behaviour leads to a Bertrand equi- librium with positive markups. We use data from an Austrian price com- parison site and find results highly compatible with Basu's theory. We can show that price points - in particular prices ending in 9 - are preva- lent and have significant impact on consumer demand. Moreover, these price points are sticky; neither the price-setter itself wants to change them neither the rivals do underbid these prices, if they represent the cheapest price on the market.e-commerce, price comparison, price policy

When private information settles the bill : money and privacy in Google's 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

Money and privacy : Android market evidence

We study the role of privacy in the market for mobile applications. For such programs used with smartphones and tablet PCs a very important market has emerged. Yet, neither the role of privacy on that market is well understood, nor do we have empirical evidence regarding its role therein. We exploit data on 300,000 mobile applications and almost 600 “applications-pairs” to analyze both sides of this market: First, we analyze the price that application suppliers charge for more privacy. Second, we study how users’ installations are related to the “personal data greediness” of mobile applications. We provide the first empirical evidence on the main assumptions of recent early models on suppliers’ and consumers’ strategies in this market. Our results show that (1) consumers take it into account when applications request rights to collect private information and (2) suppliers ask for more rights if they offer an app for free than if they offer it for a fee

Mobile applications and access to private data : the supply side of the Android ecosystem

We analyze the data collection strategies of 65,000 developers in the market for mobile applications and track 300,000 applications over four years. Many apps belong to developers with multiple apps. This fact generates variation in the privacy behaviors of the same developer for our analysis. We uncover three stylized facts: First, developers “learn” to use increasingly intrusive data strategies as they become more experienced. Second, intrusive data collection is most likely in apps that target the 13+, and 16+ age category, which raises concerns for the protection of young app consumers. Third, even within developers, critical and atypical permissions predict problematic usage of private user data most successfully. Our findings inform both regulators and scientists who wish to model supply in the market for mobile apps

ICT, search behavior and market outcomes

Information and Communication Technologies (ICT) help to reduce transaction costs in several ways. The study of this phenomenon and the resulting economic consequences are the underlying common theme in the four subsequent chapters of my dissertation. Each of them is a self-contained paper that contributes to the field of Industrial Organization. In particular, I contribute to the study of two important phenomena that arose as a consequence of the ICT-enabled reduction in transaction costs, which modern societies have seen over the last two decades: electronic commerce (E-Commerce, in what follows) and (commons based) “peer production

Spillovers in networks of user generated content : pseudo-experimental evidence on Wikipedia

I quantify spillovers of attention in a network of content pages, which is challenging, because such networks form endogenously. I exploit exogenous variation in the article network of German Wikipedia to circumvent this problem. Wikipedia prominently advertises one featured article on its main site every day, which increases viewership of the advertised article. Shifts in the viewership of adjacent articles are 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 use a difference-in-differences analysis to estimate how attention spills to neighbors through the transient shock of advertisement. I further develop an extended peer effects model which relaxes the requirement of an exogenously given network. This model enables the estimation of the underlying spillover. Advertisements affect neighboring articles substantially: Their viewership increases by almost 70 percent. This, in turn, translates to increased editing activity. Attention is the driving mechanism behind views and short edits. Both outcomes are related to the order of links, while more substantial edits are not

IT outsourcing and firm productivity : eliminating bias from selective missingness in the dependent variable

Missing values are a major problem in all econometric applications based on survey data. A standard approach assumes data are missing-at-random and uses imputation methods, or even listwise deletion. This approach is justified if item non-response does not depend on the potentially missing variables’ realization. However, assuming missing-at-random may introduce bias if non-response is, in fact, selective. Relevant applications range from financial or strategic firm-level data to individual-level data on income or privacy-sensitive behaviors. In this paper, we propose a novel approach to deal with selective item nonresponse in the model’s dependent variable. Our approach is based on instrumental variables that affect selection only through potential outcomes. In addition, we allow for endogenous regressors. We establish identification of the structural parameter and propose a simple two-step estimation procedure for it. Our estimator is consistent and robust against biases that would prevail when assuming missingness at random. We implement the estimation procedure using firm-level survey data and a binary instrumental variable to estimate the effect of outsourcing on productivity

Does Wikipedia matter? : the effect of Wikipedia on tourist choices

We analyze the impact of information on Wikipedia on tourists' choices for travel destinations. Our results suggest a strong observational correlation between the amount of content on Wikipedia and tourist overnight stays. We propose a check of whether this correlation is causal. For that, we introduce randomized exogenous variation to articles' content. While our treatment is strong enough to affect content on the treated pages positively, we find no statistically significant effect of this treatment on tourist overnight stays