Abstract
This paper develops a method to estimate the demand for network goods, using minimal network data, but leveraging within-consumer variation. I estimate demand for video games as a function of individuals’ social networks, prices, and qualities, using data from Steam, the largest video game digital distributor in the world. I separately identify price elasticities on individuals with and without friends with the same game, conditional on individual fixed effects and games’ characteristics. I then use the discrepancies between estimated price elasticities to identify the impact of social networks. I compare my method to “traditional-IV” strategies in the literature, which require detailed network data, and find similar results. A 1% increase in friends’ demands, increases demand by .13%. In counterfactual simulations, I find demand increases by about 5% from a promotional giveaway to “influencers,” those users in the top 1% of popularity in the network.
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Notes
When an individuals’ demand for a product increases with the number of others’ demand, we have a direct network effect (e.g., communication networks). In contrast, indirect network effects arise on multi-sided markets where the individuals’ demand for a product in one side of the market increases with the supply of such a product from another side of the platform, which in turn increases with individuals’ demand (e.g. online platforms). For instance, if a positive network effect is ignored, the price elasticity of demand will be overestimated, because the total effect of a price change is composed of a price effect and a network effect.
ARD refers to answers to questions of the form “how many of your links have trait X?”
Users can change their privacy settings to minimize the information shared with friends and the general public. However, users are “nudged” into public profiles.
Data and replication files can be found in the author’s website (jtudon.com) or by request. The raw data can be found in https://steam.internet.byu.edu.
In the literature, β might also be known as a peer effect, a network externality, or a consumption spillover between agents. Where appropriate, I also use the term network elasticity of demand to refer to \(\partial \log q/\partial \log n=\upbeta n/q.\)
In the peer-effects literature, the common approach is a group-level analog of Eq. 1, instead of an individual-level model.
In other words, we require repeated observations for individuals, like in this case with multi-product adoptions, in order to address selection concerns. Alternatively, as a referee pointed out, with single-product adoptions, but multiple periods of time per individual, we would require individuals consumption to be always observable to their network.
See Imbens and Angrist (1994), for example.
Always-takers represent less than 2% of the population. Table 1, “Users with friends” shows essentially summary statistics for compliers, and never-takers’ statistics are under “Users without friends”.
To boot, most of the unreported coefficients of the controls also yield estimates of the network effect around 0.9. I do not report these results, because I do not have a strong identification argument for these coefficients.
Nair (2007) reports short-run price elasticities similar to those found in this paper.
Note that from the FOC on β, \(\frac {\partial {s_{ij}}}{\partial {\upbeta }} = F^{\prime } \left (\mu _{i} -\alpha \log p_{j} + \upbeta n_{ij}+ \gamma \log r_{j} + \boldsymbol {\delta }_{0}\boldsymbol {x}_{j} \right ) \upbeta \frac {\partial {s_{ij}}}{\partial {\upbeta }}\), which does not identify β.
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Thanks to Michael Dinerstein, Ali Hortaçsu, Mauricio Romero, Adrián Rubli, and ITAM’s applied micro workshop participants. Adrián Martínez provided outstanding research assistance.
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Tudón, J. Distilling network effects from Steam. Quant Mark Econ 20, 293–312 (2022). https://doi.org/10.1007/s11129-022-09254-5
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DOI: https://doi.org/10.1007/s11129-022-09254-5