Convergence of Position Auctions under Myopic Best-Response Dynamics

Cary, Matthew, Aparna Das, Benjamin Edelman, Ioannis Giotis, Kurtis Heimerl, Anna Karlin, Scott Duke Kominers, Claire Mathieu, and Michael Schwarz. “Convergence of Position Auctions under Myopic Best-Response Dynamics.” ACM Transactions on Economics and Computation 2, no. 3 (July 2014): 1-20.

We study the dynamics of multi-round position auctions, considering both the case of exogenous click-through rates and the case in which click-through rates are determined by an endogenous consumer search process. In both contexts, we demonstrate that the dynamic auctions converge to their associated static, envy-free equilibria. Furthermore, convergence is efficient, and the entry of low-quality advertisers does not slow convergence. Because our approach predominantly relies on assumptions common in the sponsored search literature, our results suggest that dynamic position auctions converge more generally.

Pitfalls and Fraud in Online Advertising Metrics: What Makes Advertisers Vulnerable to Cheaters, and How They Can Protect Themselves

Edelman, Benjamin. “Pitfalls and Fraud in Online Advertising Metrics: What Makes Advertisers Vulnerable to Cheaters, and How They Can Protect Themselves.” Journal of Advertising Research 54, no. 2 (June 2014): 127-132.

How does online advertising become less effective than advertisers expect and less effective than measurements indicate? The current research explores problems that result, in part, from malfeasance by outside perpetrators who overstate their efforts to increase their measured performance. In parallel, similar vulnerabilities result from mistaken analysis of cause and effect–errors that have become more fundamental as advertisers target their advertisements with greater precision. In the paper that follows, the author attempts to identify the circumstances that make advertisers most vulnerable, notes adjusted contract structures that offer some protections, and explores the origins of the problems in participants’ incentives and in legal rules.

Mastering the Intermediaries: Strategies for Dealing with the Likes of Google, Amazon, and Kayak

Edelman, Benjamin. “Mastering the Intermediaries: Strategies for Dealing with the Likes of Google, Amazon, and Kayak.” Harvard Business Review 92, no. 6 (June 2014): 86-92.

Many companies depend on powerful platforms which distinctively influence buyers’ purchasing. (Consider, Google, Amazon, and myriad others in their respective spheres.) I consider implications of these platforms’ market power, then suggest strategies to help companies recapture value or at least protect themselves from abuse.

Leveraging Market Power through Tying: Does Google Behave Anti-Competitively?

Edelman, Benjamin. “Leveraging Market Power through Tying: Does Google Behave Anti-Competitively?” Harvard Business School Working Paper, No. 14-112, May 2014.

I examine Google’s pattern and practice of tying to leverage its dominance into new sectors. In particular, I show how Google used these tactics to enter numerous markets, to compel usage of its services, and often to dominate competing offerings. I explore the technical and commercial implementations of these practices, then identify their effects on competition. I conclude that Google’s tying tactics are suspect under antitrust law.

Digital Discrimination: The Case of Airbnb.com

Edelman, Benjamin, and Michael Luca. “Digital Discrimination: The Case of Airbnb.com.” Harvard Business School Working Paper, No. 14-054, January 2014.

Online marketplaces often contain information not only about products, but also about the people selling the products. In an effort to facilitate trust, many platforms encourage sellers to provide personal profiles and even to post pictures of themselves. However, these features may also facilitate discrimination based on sellers’ race, gender, age, or other aspects of appearance. In this paper, we test for racial discrimination against landlords in the online rental marketplace Airbnb.com. Using a new data set combining pictures of all New York City landlords on Airbnb with their rental prices and information about quality of the rentals, we show that non-black hosts charge approximately 12% more than black hosts for the equivalent rental. These effects are robust when controlling for all information visible in the Airbnb marketplace. These findings highlight the prevalence of discrimination in online marketplaces, suggesting an important unintended consequence of a seemingly-routine mechanism for building trust.

Price Coherence: Impact and Incentives with Julian Wright

In modern markets, buyers can often buy the same good or service directly from a seller, and through one or more intermediaries, all at the same exact price. How should buyers behave in these markets? The natural strategy is to choose whichever intermediary offers the greatest benefit — perhaps a rebate, some loyalty points, or superior service. One intermediary might charge sellers far higher fees than another. But to buyers, these fees are irrelevant since they are paid entirely by sellers. It’s a classic I-choose-you-pay situation, and buyers predictably head for high-benefit intermediaries. The resulting outcomes can be both distortionary and welfare-reducing. For example, seeing an airline’s flights available both directly on the airline’s web site and via an online travel agent (like Expedia or Orbitz) (“OTA”), a buyer has every reason to choose the latter — avoiding retyping name, address, and payment details that the OTA already has on file. Convenient as an OTA may be, few users would willingly pay the ~$3 per segment (~$12 for a standard US domestic connecting round-trip) that OTAs charge to airlines. So too for credit cards: Their rebates and points are valuable, but most consumers would prefer a ~3% discount (the fee the seller pays to the card network).

Last week Julian Wright and I posted Price Coherence and Adverse Intermediation, analyzing incentives and outcomes in affected markets. We find that price coherence reduces consumer surplus and welfare due to inflated retail prices, over-investment in providing benefits to buyers, and excessive usage of intermediaries’ services. Notably, competition among intermediaries does not fix these problems: Indeed, competition among intermediaries intensifies the problems by increasing the magnitude of the effects and broadening the circumstances in which they arise.

Our analysis is grounded in eight diverse markets: insurance brokers and financial advisors, marketplaces, cashback/rebate services, search engine advertising, real estate buyers’ agents, restaurant ordering, and restaurant reservations, plus travel booking and credit cards as discussed above. In each instance, a law, norm, intermediary policy, or similar rigidity prevents sellers from passing an intermediary’s fees to the specific buyers who choose to use that intermediary. They’re complex markets, some quite large, and each worth a look. Their key similarity: In each instance, if a buyer foregoes the corresponding intermediary, the buyer still pays a share of intermediaries’ charges for others. If a buyer places a benefit on the intermediary’s service, perhaps still far less than what the intermediary charges the seller, the buyer might as well sign up.

It may seem counterintuitive that a series of voluntary transactions leaves all parties worse off. After all, no one would willingly enter a single transaction that makes him worse off. But the interlocking relationships truly can have that effect. Returning to the airline example: Consumers use OTAs because they anticipate, correctly, that substantially all airlines are in OTAs and because consumers know that prices are equal whether buying from an OTA versus directly from an airline. With many users shopping at OTA web sites, airlines then feel compelled to offer their flights via OTAs. In general, an individual airline would not want to withhold its flights from OTAs — it would lose too many sales. And an individual consumer has no reason to book directly — no cash savings from forgoing the OTA-provided benefits. On net, both buyer and seller end up using the intermediary even when they were perfectly capable of finding each other directly and even when the intermediary’s fees exceed the value the intermediary actually provides.

Our draft:

Price Coherence and Excessive Intermediation (last updated March 2015)

(update: published as “Price Coherence and Excessive Intermediation.” Quarterly Journal of Economics 130, no. 3 (August 2015): 1283-1328.)

Competing Ad Auctions

Ashlagi, Itai, Benjamin Edelman, and Hoan Soo Lee. “Competing Ad Auctions.” Harvard Business School Working Paper, No. 10-055, January 2010. (Revised May 2010, February 2011, September 2013.)

We present a two-stage model of competing ad auctions. Search engines attract users via Cournot-style competition. Meanwhile, each advertiser must pay a participation cost to use each ad platform, and advertiser entry strategies are derived using symmetric Bayes-Nash equilibrium that lead to the VCG outcome of the ad auctions. Consistent with our model of participation costs, we find empirical evidence that multi-homing advertisers are larger than single-homing advertisers. We then link our model to search engine market conditions: We derive comparative statics on consumer choice parameters, presenting relationships between market share, quality, and user welfare. We also analyze the prospect of joining auctions to mitigate participation costs, and we characterize when such joins do and do not increase welfare.

Earnings and Ratings at Google Answers

Edelman, Benjamin. “Earnings and Ratings at Google Answers.” Economic Inquiry 50, no. 2 (April 2012): 309-320. (draft as first circulated in 2004.)

I analyze all questions and answers from the inception of the Google Answers service through November 2003, and I find notable trends in answerer behavior: more experienced answerers provide answers with the characteristics askers most value, receiving higher ratings as a result. Answerer earnings increase in experience, consistent with learning on the job. Answerers who focus on particular question categories provide answers of higher quality but earn lower pay per hour (perhaps reflecting a lack of versatility). Answers provided during the business day receive higher payments per hour (a compensating differential for working when outside options are most attractive), but more experienced answerers tend to forego these opportunities.

Advertising Disclosures: Measuring Labeling Alternatives in Internet Search Engines

Edelman, Benjamin, and Duncan S. Gilchrist. “Advertising Disclosures: Measuring Labeling Alternatives in Internet Search Engines.” Information Economics and Policy 24, no. 1 (March 2012): 75-89.

In an online experiment, we measure users’ interactions with search engines, both in standard configurations and in modified versions with clearer labels identifying search engine advertisements. In particular, for a random subset of users, we change “Sponsored links” or “Ads” labels to instead read “Paid Advertisements.” Relative to users receiving the “Sponsored link” or “Ad” labels, users receiving the “Paid Advertisement” label click 25% and 27% fewer advertisements, respectively. Users seeing “Paid Advertisement” labels also correctly report that they click fewer advertisements, controlling for the number of advertisements they actually click. Results are most pronounced for commercial searches and for vulnerable users with low education and little online experience.

Using Internet Data for Economic Research

Edelman, Benjamin. “Using Internet Data for Economic Research.” Journal of Economic Perspectives 26, no. 2 (Spring 2012): 189-206.

The data used by economists can be broadly divided into two categories. First, structured datasets arise when a government agency, trade association, or company can justify the expense of assembling records. The Internet has transformed how economists interact with these datasets by lowering the cost of storing, updating, distributing, finding, and retrieving this information. Second, some economic researchers affirmatively collect data of interest. Historically, assembling a dataset might involve delving through annual reports or archives that had not previously been organized into a format ready for research: in some cases, surveying stores, factories, consumers, or workers, or in other cases, carrying out an experiment. For researcher-collected data, the Internet opens exceptional possibilities both by increasing the amount of information available for researchers to gather and by lowering researchers’ costs of collecting information. In this paper, I explore the Internet’s new datasets, present methods for harnessing their wealth, and survey a sampling of the research questions these data help to answer.