The Future of Weak Ties

“The Strength of Weak Ties” (Granovetter 1973) arguably contains the most influential sociological theory of networks. Granovetter’s subtle, nuanced theory has spawned countless follow-on ideas, many of which are immortalized in the 35,000 manuscripts that cite the original work. Among these are notable theories in their own right, such as Ron Burt’s structural holes theory (Burt 1992), which itself has generated a sizable body of knowledge about the social structure of competition

Networked Experiments

This chapter considers the design and analysis of networked experiments, one of the most precise tools available for studying social behavior. As a result of digitization, the scale, scope and complexity of networked experiments have expanded significantly in recent years, creating a need for more robust design and analysis strategies. I first review innovations in networked experimental design, assessing the implications of the experimental setting, sampling, randomization procedures and treatment assignment. I then discuss the analysis of networked experiments, with particular emphasis on modeling treatment response assumptions, inference and estimation, and recent approaches to interference and uncertainty in dependent data. I conclude by discussing important challenges facing the future of networked experimentation, focusing on adaptive treatment assignment, novel randomization techniques, linking online treatments to offline responses and experimental validation of observational methods. I hope this framework can help guide future work toward a cumulative research tradition in networked experimentation

Mitochondrial DNA common deletion is not associated with thyroid, breast and colorectal tumors in Turkish patients

Recently, efforts have been focused on mitochondrial DNA changes and their relation to human cancers. Among them, a 4977 bp deletion of mitochondrial DNA, named “common deletion”, has been investigated in several types of tumors, with inconsistent results. In this study, we investigated the presence of the common deletion in tissues from 25 breast, 25 colorectal and 50 thyroid tumors and in the adjacent healthy tissues from Turkish patients. Samples from healthy volunteers were also evaluated for comparison. Two PCR-based methods were used for the detection of the common deletion. First, two pairs of primers were used to amplify wild-type and deleted mtDNA. Then, a highly sensitive nested-PCR was performed, to determine low amounts of deleted genomes. By the first method, wild-type mtDNAs were observed in all samples, but a deletion was observed in only six thyroid samples, by using the nested-PCR method. In conclusion, the mitochondrial common deletion was very rare in our study group and did not appear to be not related with cancer

Exercise contagion in a global social network

We leveraged exogenous variation in weather patterns across geographies to identify social contagion in exercise behaviours across a global social network. We estimated these contagion effects by combining daily global weather data, which creates exogenous variation in running among friends, with data on the network ties and daily exercise patterns of ∼1.1M individuals who ran over 350M km in a global social network over 5 years. Here we show that exercise is socially contagious and that its contagiousness varies with the relative activity of and gender relationships between friends. Less active runners influence more active runners, but not the reverse. Both men and women influence men, while only women influence other women. While the Embeddedness and Structural Diversity theories of social contagion explain the influence effects we observe, the Complex Contagion theory does not. These results suggest interventions that account for social contagion will spread behaviour change more effectively.National Science Foundation (U.S.) (0953832

Digital Paywall Design: Implications for Content Demand and Subscriptions

Most online content publishers have moved to subscription-based business models regulated by digital paywalls. But the managerial implications of such freemium content offerings are not well understood. We, therefore, utilized microlevel user activity data from the New York Times to conduct a large-scale study of the implications of digital paywall design for publishers. Specifically, we use a quasi-experiment that varied the (1) quantity (the number of free articles) and (2) exclusivity (the number of available sections) of free content available through the paywall to investigate the effects of paywall design on content demand, subscriptions, and total revenue. The paywall policy changes we studied suppressed total content demand by about 9.9%, reducing total advertising revenue. However, this decrease was more than offset by increased subscription revenue as the policy change led to a 31% increase in total subscriptions during our seven-month study, yielding net positive revenues of over $230,000. The results confirm an economically significant impact of the newspaper’s paywall design on content demand, subscriptions, and net revenue. Our findings can help structure the scientific discussion about digital paywall design and help managers optimize digital paywalls to maximize readership, revenue, and profit

Engineering social contagions: Optimal network seeding in the presence of homophily

We use data on a real, large-scale social network of 27 million individuals interacting daily, together with the day-by-day adoption of a new mobile service product, to inform, build, and analyze data-driven simulations of the effectiveness of seeding (network targeting) strategies under different social conditions. Three main results emerge from our simulations. First, failure to consider homophily creates significant overestimation of the effectiveness of seeding strategies, casting doubt on conclusions drawn by simulation studies that do not model homophily. Second, seeding is constrained by the small fraction of potential influencers that exist in the network. We find that seeding more than 0.2% of the population is wasteful because the gain from their adoption is lower than the gain from their natural adoption (without seeding). Third, seeding is more effective in the presence of greater social influence. Stronger peer influence creates a greater than additive effect when combined with seeding. Our findings call into question some conventional wisdom about these strategies and suggest that their overall effectiveness may be overestimated. keywords: peer influence; social contagion; social networks; viral marketing; information systems; simulatio

Social Advertising Effectiveness Across Products: A Large-Scale Field Experiment

Most of the empirical evidence on social advertising effectiveness focuses on a single product at a time. As a result, little is known about how the effectiveness of social advertising varies across product categories or product characteristics. We therefore collaborated with a large online social network to conduct a randomized field experiment measuring social ad effectiveness across 71 products in 25 categories among more than 37 million users. We found some product categories, like clothing, cars, and food, exhibited significantly stronger social advertising effectiveness than other categories, like financial services, electrical appliances, and mobile games. More generally, we found that status goods, which rely on status-driven consumption, displayed strong social advertising effectiveness. Meanwhile, social ads for experience goods, which rely on informational social influence, did not perform any better or worse than social ads for their theoretical counterparts, search goods. Social advertising effectiveness also significantly varied across the relative characteristics of ad viewers and their friends shown in ads. Understanding the heterogeneous effects of social advertising across products can help marketers differentiate their social advertising strategies and lead researchers to more nuanced theories of social influence in product evaluation