Working Papers
Display Advertising Pricing in Exchange Markets
with Carl Mela
Job Market Paper

This paper considers how a publisher (e.g., Wall Street Journal) should set reserve prices for real-time bidding (RTB) auctions when selling display advertising impressions through ad exchanges, a $40 billion market and growing. Through a series of field experiments, we find that setting the reserve price increases publisher’s revenues by 32%, thereby affirming the importance of reserve price in maximizing publisher’s revenues from auctions. Further, we find that advertisers increase their bids in response to an experimental increase in reserve price, and show this behavior is consistent with the use of a minimum impression constraint to ensure advertising reach.
Based on this insight, we construct an advertiser bidding model and use it to infer the overall demand curve for advertising as a function of reserve prices. Using this demand model, we solve the publisher pricing problem. Incorporating the minimum impression constraint into the reserve price setting process yields a 50% increase over a solution that does not incorporate the constraint, and an additional increase in profits of nine percentage points.

Monetizing Online Marketplaces
with Carl Mela
Revising for 2nd round at Marketing Science
MSI Working Paper Series No. 18-112-05
Previously titled "Online Marketplace Advertising"

This paper considers the monetization of online marketplaces. These platforms trade-off fees from advertising with commissions from product sales. While featuring advertised products can make search less efficient (lowering transaction commissions), it incentivizes sellers to compete for better placements via advertising (increasing advertising fees). We consider this trade-off by modeling both sides of the platform. On the demand side, we develop a joint model of browsing (impressions), clicking, and purchase. On the supply side, we consider sellers’ valuation and advertising competition under various fee structures (CPM, CPC, CPA) and ranking algorithms.
Using buyer, seller, and platform data from an online marketplace where advertising dollars affect the order of seller items listed, we find that ranking items by consumer utility lowers platform’s profits as it leads to more lower price item purchases. Combining a ranking algorithm that sorts items by expected sales revenue with a CPC auction limited to the top 5 positions improves profits the most, because this practice monetizes the highest valuations for advertising on top, while enhancing the transaction revenues in the lower positions.

Online Display Advertising Markets: A Literature Review and Future Directions
with Carl Mela, Santiago Balseiro, and Adam Leary
Revising for 2nd round at Information Systems Research
Columbia Business School Research Paper No. 18-1

This paper considers how publishers’ ad inventory pricing decisions, the allocation of ad inventory across distribution channels (direct/exchange channels), and the amount of customer information it shares with the advertisers affect its revenues in display advertising markets. Focusing on the first question, and in particular setting the optimal reserve price in the exchange channel, a series of field experiments show that setting the reserve price can increase publisher’s revenues substantially (32%). Further, we find that advertisers appear to behave as if they face minimum impressions constraint and deviate from truth-telling. Based on this insight, an advertiser bidding model is constructed to incorporate the minimum impressions goal. The optimal reserve price with the minimum impressions constraint is computed and the magnitude of the profit loss in ignoring this constraint is assessed. Subsequent iterations of this research will address the remaining allocation and information provision questions.

Work in Progress
Display Advertising Pricing, Allocation, and Information Sharing in Dual Channel
with Carl Mela
Data collected, analysis in progress

A publisher in a display ad market sells its advertising inventory both via ad exchange auctions and via direct sales. Ad exchanges (e.g., DoubleClick Ad Exchange) are centralized marketplaces where publishers supply and advertisers demand display advertising impressions in real-time bidding (RTB) auctions. The direct sale involves the advance sale of a bundle of ad impressions directly to the advertiser at a fixed price. The important research questions are then i) how ad inventories should be priced (fixed price in the direct sale and the reserve price in the exchange channel), ii) how ad inventories should be allocated across distribution channels (direct or exchanges first), and iii) how much information should be revealed to advertisers about specific ad impressions.
Based on a two-stage game theory model, we show that the equilibrium channel choice depends on the coefficient of variation (CV) of the valuation distribution. Advertisers with higher CV prefer the exchange over the direct channel because the value of information revealed in the ad exchange (e.g., cookie) is high and they have a higher option value of waiting. We are extending this theoretical framework to an empirical context with the novel dataset collected both for the direct and the exchange channels from a large, premium publisher, ranked within U.S. top 10.

Long-Term Effect of SMS Retargeting: Balancing Opt-Out and Short-Term Direct Responses
Data collected, analysis in progress

E-commerce platforms, including online marketplaces, often send out SMS messages for advertising and promotions. Using a large-scale dataset involving natural experiments, I find that SMS messages increase the average purchase amount significantly (i.e., short-term direct responses); but at the same time, they also increase consumers’ opting-out of marketing communications. I also find that less than 1% of consumers opt back in after making these opt-out decisions. Therefore, I examine the optimal SMS targeting strategy to maximize the long-term gain by considering both the rate of opt-out decisions and the effects on short-term direct responses.