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The Extent to Which Your Friends’ Behavior Predicts Your Own

Some cool insights below from Decision Science News.

Prior to this study, advertisers have been unable to demonstrate (with statistical support) that a link can be made from a social network and product service adoption. The main findings, if you're pressed for time and would like to avoid the text below, are (1) consumers linked to a prior customer adopt the service at a rate 3-5 times greater than baseline groups and (2) analyzing social networks allows companies to target to consumers who otherwise would have fallen through the cracks, because they would not have been identified based on traditional attributes.


We measured the extent to which your friends’ behavior predicts your own, and found that in several consumer domains the effect is substantial, complementing traditional demographic and behavioral predictors.

we merged a large social network (based on email and IM exchanges) with offline sales data at an upscale, national department store chain. Thus, for each of over one million users, we had their past purchase amounts in dollars, and had the same information for each of their network contacts. Think about this for a minute: we not only know how much these individuals themselves spent at an offline retailer, but also how much their social contacts spent, a testament to how profoundly the Internet is changing the way we study human behavior.

The plot below summarizes our findings. First, as indicated by the top line, consumers whose friends spent a lot, also spent a lot themselves, consistent with the hypothesis that homophily extends to consumer behavior. When friends (alters) on average spent $400 during the six-month observation period, the consumer herself (ego) spent nearly $600, more than twice the typical consumer (indicated by the dotted line). As our aim is prediction, however, the relevant question is not just whether friends are similar in their purchasing behavior, but rather how much information is conveyed by social ties relative to other attributes. One might conjecture that ties simply indicate demographic (i.e., age and sex) similarity, that those who spend a lot are more likely to be middle-aged women—the primary market segment for this department store—and that friends of middle-aged women tend also to be middle-aged women. To test this hypothesis, we first paired each individual with a randomly chosen consumer of identical age and sex. The bottom line shows that this demographically matched group is, perhaps surprisingly, pretty ordinary. In other words, looking only at age and sex, you can’t identify consumers whose friends spend a lot (and who we know spend a lot themselves).

Though it’s standard marketing practice to target consumers based on their demographics, it’s an admittedly noisy profiling technique. So, to put social through the wringer, we next took the “socially select” group—consumers whose friends spent a lot—and matched them to random consumers with identical age, sex and past purchases. Each social candidate, that is, was matched to a consumer not only of the same age and sex, but one who spent approximately the same amount as the social candidate during the previous six months. Even relative to this formidable baseline, social cues still provide considerable information. As the middle line indicates, knowing a consumer’s age, sex and past purchases, but not that their friends are shopaholics, one would still underestimate their future sales.

We repeated this analysis for two other domains—examining signups for Yahoo! Fantasy Football, and clicks on ten online banner ads for movies, apparel, government programs, and beyond—again finding that the predictive power of social persists even after adjusting for age, sex, and past behavior. Lest you run off to rejigger your social strategy (leverage the social graph to deliver personalized experiences, anyone?), we should mention a couple of caveats. First, we have shown that consumers with big-spending friends tend to spend a lot—more, in fact, than demographics and past purchases alone would suggest. But since most people, even premium customers, don’t have shopaholic friends, social cues do not substantially boost average predictive performance. Second, though social signals help predict how much consumers spend, they don’t always help identify which consumers will spend the most. Those who recently spent fifty grand on sartorial elegance are likely to be habitual top spenders, regardless of what you know about their friends.

Still curious? Read the rest or the entire paper.


Network-based marketing refers to a collection of marketing techniques that take advantage of links between consumers to increase sales. We concentrate on the consumer networks formed using direct interactions (e.g., communications) between consumers. We survey the diverse literature on such marketing with an emphasis on the statistical methods used and the data to which these methods have been applied. We also provide a discussion of challenges and opportunities for this burgeoning research topic. Our survey highlights a gap in the literature. Because of inadequate data, prior studies have not been able to provide direct, statistical support for the hypothesis that network linkage can directly affect product/service adoption. Using a new data set that represents the adoption of a new telecommunications service, we show very strong support for the hypothesis. Specifically, we show three main results: (1) “Network neighbors”—those consumers linked to a prior customer—adopt the service at a rate 3–5 times greater than baseline groups selected by the best practices of the firm’s marketing team. In addition, analyzing the network allows the firm to acquire new customers who otherwise would have fallen through the cracks, because they would not have been identified based on traditional attributes. (2) Statistical models, built with a very large amount of geographic, demographic and prior purchase data, are significantly and substantially improved by including network information. (3) More detailed network information allows the ranking of the network neighbors so as to permit the selection of small sets of individuals with very high probabilities of adoption.