Benjamin G. Edelman

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Uncovering Racial Discrimination in the ‘Sharing Economy’

New research by Benjamin G. Edelman and Michael Luca shows how online marketplaces like Airbnb inadvertently fuel racial discrimination. Open for comment; 1 Comment posted.

The Tricky Business of Managing Web Advertising Affiliates

Advertising through numerous website affiliates potentially helps marketers get more bang for their buck. But the far-flung systems can also lead to fraud, says Ben Edelman. What's the best way to manage your advertising network? Open for comment; 2 Comments posted.

Digital Discrimination: The Case of

To build trust and facilitate transactions, online marketplaces present information not only about products, but also about the people offering the products. Many platforms now allow sellers to present personal profiles, post pictures of themselves, and even link to their Facebook accounts. While these features serve the laudable goals of building trust and accountability, they can also bring unintended consequences: Personal profiles may facilitate discrimination. Benjamin G. Edelman and Michael Luca investigate the extent of racial discrimination against hosts on the popular online rental marketplace They construct a data set combining pictures of all New York City landlords on Airbnb with their rental prices and information about characteristics and quality of their properties. The authors use this data to measure differences in outcomes according to host race. Nonblack hosts are able to charge approximately 12 percent more than black hosts, holding location, rental characteristics, and quality constant. Moreover, black hosts receive a larger price penalty for having a poor location relative to nonblack hosts. These differences highlight the risk of discrimination in online marketplaces, suggesting an important unintended consequence of a seemingly-routine mechanism for building trust. Read More

Price Coherence and Adverse Intermediation

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. Buyers respond by choosing whichever intermediary offers the greatest benefit - perhaps a rebate, some kind of "points," or superior service. Importantly, buyers ignore the fees that intermediaries charge to sellers. The resulting outcomes can be distortionary and welfare-reducing. In particular, as intermediaries compete to attract buyers, they can set benefit levels so high that no net value is created and, sometimes, that buyers and seller would be jointly better off without intermediaries. The study examines six markets in which intermediaries are prominent: travel booking networks, credit and debit cards, insurance brokers and financial advisors, malls and marketplaces (such as Amazon Marketplace), cashback and rebate services, and search engine advertising. 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. Read More

Information and Incentives in Online Affiliate Marketing

Compared to historic advertising methods, online marketing invites advertisers to attempt a sharply increased quantity of partnerships. Online relationships reduce the transaction costs of buying ad placements. In many advertising marketplaces, standardized contracts let an advertiser accept a proposed placement with a single click, and ad networks widely sell bundles of hundreds or thousands of placements. Meanwhile, many advertisers find they can get valuable leads and favorable pricing from the Internet's myriad small sites. These numerous relationships entail costs, too, such as selecting, compensating, and supervising the sites, making sure each site is suitable to show the advertiser's offer, and making sure sites in fact deliver the promised benefits. Advertisers thus turn to specialists and outside firms to handle important aspects of advertising-buying. In this paper, the authors evaluate advertisers' chosen management structures by measuring the relative prevalence of advertising fraud targeting advertisers engaged in online "affiliate marketing," a performance-based compensation system increasingly common in online ad campaigns. Specifically, the authors identify the vulnerabilities best addressed by outsourcing marketing management to external specialists, versus the problems better overseen by keeping management decisions in-house. They find outside advisors most effective at enforcing clear rules, but in-house staff excel at preventing practices viewed as "borderline" under industry norms. While the results apply most directly to advertisers considering the management structure of their online marketing programs, the analysis also speaks to broader concerns of outsourcing and the boundary of the firm. Read More

Exclusive Preferential Placement as Search Diversion: Evidence from Flight Search

Measuring the net effect of search diversion is important for understanding the extent to which search engines and other intermediaries may act to influence consumer behavior. This paper makes two contributions. First, the authors develop a theoretical model to establish conditions when a search engine chooses to divert search to a less relevant service. Results indicate that search engines have a larger incentive to divert search when they are able to alter the consumers' perceptions of the difference between non-paid and paid placements, and when search engines place a large weight on revenue. These results are consistent with instances where some search engines have labeled paid links with confusing euphemisms or not at all, and where some search engines have mixed paid and non-paid links in the same area of the screen. Second, the authors measure the impact of a diversion mechanism where a search engine exclusively awards a non-paid preferred placement slot to its own service. Specifically, they examine Google's preferred placement of Flight Search. Analysis indicates that there was an 85 percent increase in click-through rates for paid advertising and a 65 percent decrease in click-through rates for non-paid algorithmic search traffic to competing online travel agencies. Both changes are statistically significant, providing evidence of Google's ability to influence how consumers choose services after they search. Read More

Sharpening Your Skills: Online Marketing

In this collection from our archives, Harvard Business School faculty discuss the latest research on online marketing techniques, including consumer reviews, video ads, loyalty programs, and coupon offerings. Open for comment; 6 Comments posted.

Pricing and Efficiency in the Market for IP Addresses

Every device connected to the Internet—from PCs to tablets, printers to cash registers—needs an IP address. The current addressing standard, IPv4, uses addresses with 32 binary digits, allowing approximately 4 billion IP addresses. The world's centralized supply of unused IP addresses reached exhaustion in February 2011, and networks in most countries will soon find they cannot easily obtain additional IPv4 addresses. While addresses may now be bought and sold, the institutions and rules of these transfers are not yet well-developed. Nor have economic models examined the unusual characteristics of this market. Benjamin Edelman and Michael Schwarz model the market for IPv4 addresses, including evaluating novel rules intended to avoid possible harms from the purchase and sale of IP addresses, as well as predicting price trends. Read More

The Yelp Factor: Are Consumer Reviews Good for Business?

In a new study, Assistant Professor Michael Luca shows just how much restaurant reviews on Yelp affect companies' bottom lines. The more difficult question: Are these ratings reliable as a measure of product quality? Closed for comment; 14 Comments posted.

To Groupon or Not to Groupon: The Profitability of Deep Discounts

For consumers, online discount vouchers (like those offered by have obvious appeal: discounts as large as 90 percent. But for retailers offering the deals through the site, does the publicity compensate for the deep hit to profit margins? This paper sets out to help small businesses decide whether it makes sense to offer discount vouchers. Research was conducted by Harvard Business School professor Ben Edelman, Business Economics PhD candidate Scott Duke Kominers, and by Sonia Jaffe of the Harvard University Department of Economics. Read More

HBS Faculty Comment on Environmental Issues for Earth Day

Harvard Business School faculty members offer their views on the many business facets of "going green." Open for comment; 4 Comments posted.

Is Groupon Good for Retailers?

For retailers offering deals through the wildly popular online start-up Groupon, does the one-day publicity compensate for the deep hit to profit margins? A new working paper, "To Groupon or Not to Groupon," sets out to help small businesses decide. Harvard Business School professor Benjamin G. Edelman discusses the paper's findings. Closed for comment; 59 Comments posted.

Sponsored Links’ or ’Advertisements’?: Measuring Labeling Alternatives in Internet Search Engines

In processing a search for a particular phrase, Internet search engines generally offer two types of results: the algorithmic results, which a search engine selects based on relevance, and the "sponsored links," for which advertisers pay. The latter often occupy prominent screen space. But does the average web surfer realize that they are advertisements? In an online experiment, Harvard Business School professor Benjamin Edelman and doctoral candidate Duncan S. Gilchrist show that "sponsored link" is too vague a term for some users to understand, and that "paid advertisement" is a label that better clarifies the nature of the link. They call on the FTC to compel search engines to improve their disclosures. Read More

Competing Ad Auctions

Joining ad platforms can attract substantial regulatory attention: In November 2008, the Department of Justice planned to file antitrust charges to stop the proposed Google-Yahoo transaction. More recently, in September 2009, the Department of Justice sought additional information from Microsoft and Yahoo about their proposed partnership. At first glance it might seem paradoxical to claim that the Google-Yahoo transaction is undesirable, for advertisers and for the economy as a whole, while the Microsoft-Yahoo transaction offers net benefits. But that conclusion is entirely possible. HBS professor Benjamin G. Edelman and doctoral candidates Itai Ashlagi and Hoan Soo Lee explore competition among ad platforms that offer search engine advertising services. In addition, the authors evaluate possible transactions among ad platforms—building tools to predict which transactions improve welfare and which impede it. Read More

Optimal Auction Design and Equilibrium Selection in Sponsored Search Auctions

Reserve prices may have an important impact on search advertising marketplaces. But the effect of reserve prices can be opaque, particularly because it is not always straightforward to compare "before" and "after" conditions. HBS professor Benjamin G. Edelman and Yahoo's Michael Schwarz use a pair of mathematical models to predict responses to reserve prices and understand which advertisers end up paying more. Read More

Can Entrepreneurs Drive People Movers to Success?

Call them next-generation driverless taxis or people movers, the age of personal rapid transport is just around the bend. Could PRT change the face of public transportation in cities and smaller communities? HBS professor Benjamin G. Edelman weighs the benefits and opportunities for entrepreneurs and for society. "Right now, the field is wide open," he says. Read More

Demographics, Career Concerns or Social Comparison: Who Games SSRN Download Counts?

Why do certain individuals commit fraudulent acts—in this case repeatedly downloading their own working papers from the Social Science Research Network (SSRN) repository to increase the papers' reported download counts? HBS professors Benjamin G. Edelman and Ian I. Larkin study the relative importance of demographic, economic, and psychological factors leading individuals to commit this kind of gaming. Authors engage in deceptive self-downloading to improve a paper's visibility on SSRN, to obtain more favorable assessments of paper quality, and to obtain possible benefits for promotion and tenure decisions at those schools that consider download counts in tenure decisions. Data indicates that authors are more likely to inflate their papers' download counts when a higher count greatly improves the visibility of a paper on the SSRN network. Authors are also more likely to inflate their papers' download counts when their peers recently had successful papers—suggesting an "envy" effect in download gaming. Download inflations are also affected somewhat by career concerns (e.g. just before changing jobs) and by demographic factors, though these effects are smaller. On the whole, analysis suggests a heightened risk of fraudulent acts not only where economic returns are high, but also where prestige, status, or reputation are important. Read More

Running Out of Numbers: Scarcity of IP Addresses and What To Do About It

Hidden from view of typical users, every Internet communication relies on an underlying system of numbers to identify data sources and destinations. Users typically specify online destinations by entering domain names (e.g. ""). But the Internet's routers forward data according to numeric IP addresses (e.g. To date, the Internet has enjoyed an ample supply of "IPv4" IP addresses, but demand is substantial and growing. Current allocation rates suggest IPv4 exhaustion by approximately 2011. A new numbering system, IPv6, would relieve scarcity, but incentives hinder transition: IPv4 works well for existing networks, and offers easier and simpler access to existing Internet content and services. As a result, to date few networks have begun to support v6. In principle regulators could order networks to implement v6, but the applicable Internet coordinating organizations lack authority or power to force such a transition. In the meantime, a market mechanism for v4 addresses offers important benefits, including allocating scarce v4 addresses to those who need them most, and putting a positive price on v4 space in order to encourage transition to v6. Thus, it seems v4 transfers can help both to mitigate the worst effects of v4 scarcity, and to build the incentives necessary for transition to v6. Read More

When the Internet Runs Out of IP Addresses

Experts predict that within three years we will see the last of new Web addresses. What will happen then? The best solution is to create a market for already assigned but unwanted numbers, says Harvard Business School professor Ben Edelman. Read More

CPC/CPA Hybrid Bidding in a Second Price Auction

How should online advertisers measure and pay for advertising deliveries? Options include pay per impression (CPM), per click (CPC), per action (CPA), or in proportion of the dollar value of merchandise sold. The advertisers who choose to pay one way may differ, systematically, from those who choose to pay in some other way. HBS professor Benjamin Edelman and doctoral student Hoan Soo Lee present the problem in an algebraic model in anticipation of measurement to follow in future work. Read More

Securing Online Advertising: Rustlers and Sheriffs in the New Wild West

Online advertising remains a "Wild West" where users are faced with ads they ought not believe and where firms overpay for ads without getting the results they were promised. But it doesn't have to be this way. Enforcement by public agencies is starting to remind advertisers and ad networks that long-standing consumer protection rules still apply online. And as advertisers become more sophisticated, they're less likely to tolerate opaque charges for services they can't confirm they received. During the past five years, Edelman has uncovered hundreds of online advertising scams defrauding thousands of users, including all the Web's top merchants. This chapter summarizes some of what he has found and what users and advertisers can do to protect themselves. Read More

Google-Yahoo Ad Deal is Bad for Online Advertising

A proposed advertising deal between Internet competitors Google and Yahoo would reduce competitiveness in the Internet advertising market, likely resulting in higher advertising rates, says Harvard Business School professor Benjamin G. Edelman. Read More

Optimal Deterrence when Judgment-Proof Agents Are Paid In Arrears—With an Application to Online Advertising Fraud

It is commonplace for large entities (both advertisers and ad networks) to enter into relationships with numerous small agents such as Web sites, blogs, search syndicators, and other marketing partners. For example, one well-known affiliate network boasts more than a million affiliates promoting offers from the network's hundreds of merchants, and Google contracts with numerous independent Web sites to show Google's "AdSense" ads. Although these advertising agents are often small, they can take advantage of technology to claim payments they have not earned. In practice, the legal system cannot offer meaningful redress to an aggrieved advertiser or ad network. This paper argues that delayed payment offers a more expedient alternative—a sensible stopgap strategy for use when primary enforcement systems prove inadequate. Read More

Reducing Risk with Online Advertising

Fraud is fairly easy in the world of online advertising, particularly for determined adversaries. In this Q&A, HBS professor Ben Edelman, who designs electronic markets, explains how contract terms can be managed to both reduce advertisers' risks of being defrauded and reward good suppliers. "The idea here is to make everyone better off, except of course the fraudsters," Edelman says. Read More

On Best-Response Bidding in GSP Auctions

Keyword auctions have become a critical source of revenue for Google and Yahoo!, among others. This new form of advertising has provided a new way for advertisers to reach customers. But advertisers also face the complex task of optimizing bids to increase their exposure while avoiding unnecessary costs. HBS professor Benjamin Edelman and colleagues analyzed a class of bidding strategies that attempt to increase advertiser utility under limited assumptions about other players' behavior. Under a strategy they call Balanced Bidding (BB), advertisers converge to the advertiser-preferred equilibrium—achieving stability of bids and reducing advertisers' costs relative to other possible outcomes. Read More