Chris Nosko

A growing body of empirical literature finds that consumers are relatively limited in how much they search over product characteristics. We assemble a dataset of search and purchase behavior from eBay to quantify the returns, and thus implied costs, to consumer search on the internet. The extensive nature of the eBay data allows us to examine a rich and detailed set of questions related to search in a way that previous structural models cannot. In contrast to the literature, we find that consumers search a lot: on average 36 times per purchase over 3 (distinct) days, with most sessions ending in no purchase. We find that search costs are relatively low, in the region of 25 cents per search page. We pursue the analysis further by, i) examining how users refine their search, ii) how sear...

We argue that reputation mechanisms used by platform markets suffer from two problems. First, buyers may draw conclusions about the quality of the platform from single transactions, causing a reputational externality across sellers. Second, for a variety of reasons we discuss, reputations will be biased. We document these problems using eBay data and claim that platforms can benefit from identifying and promoting higher quality sellers. We create an unobservable measure of seller quality and demonstrate the benefits of our approach through a controlled experiment that prioritizes better quality sellers. We highlight the importance of reputational externalities and chart an agenda that aims to create more realistic models of platform markets.

Internet advertising has been the fastest growing advertising channel in recent years with paid search ads comprising the bulk of this revenue. We present results from a series of large scale field experiments done at eBay that were designed to measure the causal effectiveness of paid search ads. Because search clicks and purchase behavior are correlated, we show that returns from paid search are a fraction of conventional non-experimental estimates. As an extreme case, we show that brand-keyword ads have no measurable short-term benefits. For non-brand keywords we find that new and infrequent users are positively influenced by ads but that more frequent users whose purchasing behavior is not influenced by ads account for most of the advertising expenses, resulting in average returns that ...

Published: Thomas Blake & Chris Nosko & Steven Tadelis, 2015. "Consumer Heterogeneity and Paid Search Effectiveness: A Large‐Scale Field Experiment," Econometrica, Econometric Society, vol. 83, pages 155-174, 01. citation courtesy of

Changes in technologies for reproducing and redistributing digital goods (e.g., music, movies, software, books) have dramatically affected profitability of these goods, and raised concerns for future development of socially valuable digital products. However, broader illegitimate distribution of digital goods may have offsetting demand implications for legitimate sales of complementary non-digital products. We examine the negative impact of file-sharing on recorded music sales and offsetting implications for live concert performances. We find that file-sharing reduces album sales but increases live performance revenues for small artists, perhaps through increased awareness. The impact on live performance revenues for large, well-known artists is negligible.

Published: Mortimer, Julie Holland & Nosko, Chris & Sorensen, Alan, 2012. "Supply responses to digital distribution: Recorded music and live performances," Information Economics and Policy, Elsevier, vol. 24(1), pages 3-14. citation courtesy of