Quantity Versus Quality: Experimenting with the Margins for Social Information

People share their experiences of goods and services online, through reviews, ratings and endorsements on social networks, potentially generating welfare-improving information that can help subsequent consumers make better, more informed decisions. While the economics literature has focused on questions of alignment and the intensive quality of provided information, another tension is extensive: in the absence of an incentive, many might choose not to provide information at all. We study three different incentives that encourage information transmission on the extensive margin, examining the tradeoffs between quality and quantity of information. Our findings indicate substantial efficiency gains can be made relative to no incentives, even when the incentives damage the preference alignment between those sending and receiving information. In particular, our results point to a partially aligned incentive (similar to a referral or sales commission) as robustly encouraging the provision of information while not producing substantial reductions in quality

Reciprocity through ratings: An experimental study of bias in evaluations

This paper studies the potential for ratings of seller quality to be influenced by side payments to raters. In a laboratory setting, we find that even modest side payments from sellers to raters have large effects, with the type of rating (favorable or unfavorable) given to a seller determined primarily by how large a monetary transfer the seller makes to the rater. Our results demonstrate that side payments can crowd out a rater’s concern for buyers, even in situations where there is no potential for long-term relationship building

Living a Lie: Theory and Evidence on Public Preference Falsification

We propose a model of how public behavior changes in response to the evolution of privately held preferences. Our aim is to rationalize the tendency for individuals who hold minority viewpoints to falsely report their preferences by taking actions favored by the majority. We do this using a game involving a tension between honest expression of one’s true preferences and a desire to conform to the behavior of others. In an experimental test of our model, we find confirmatory support for the model’s main predictions, that even after a majority of the population shares what was previously an unpopular minority opinion, a lack of mutual awareness among members of the new majority can allow continued public support for the old status quo, and that the onset and speed of transitions to new, majority-held opinions depend on the relative difference in rewards from conformity versus truthful expressio

All Nash Equilibria of the Multi-Unit Vickrey Auction

This paper completely characterizes the set of Nash equilibria of the Vickrey auction for multiple identical units when buyers have non-increasing marginal valuations and there at least three potential buyers. There are two types of equilibria: In the first class of equilibria there are positive bids below the maximum valuation. In this class, above a threshold value all bidders bid truthfully on all units. One of the bidders bids at the threshold for any unit for which his valuation is below the threshold; the other bidders bid zero in this range. In the second class of equilibria there are as many bids at or above the maximum valuation as there are units. The allocation of these bids is arbitrary across bidders. All the remaining bids equal zero. With any positive reserve price equilibrium becomes unique: Bidders bid truthfully on all units for which their valuation exceeds the reserve price

Three Essays On Online Ratings and Auction Theory

This work includes three papers, focusing on online ratings and auction theory. The first chapter, "Why Do People Write Reviews? Theory and Evidence on Online Ratings" examines what motivates consumers to provide uncompensated ratings for products on in the internet. It finds that both a desire to inform other buyers and to punish or reward sellers are at play.The second chapter "All Equilibria of the Multi-Unit Vickrey Auction" characterizes all Nash Equilibria for the Vickrey auction with three or more bidders and any number of units. It shows that all equilibria fall into one of two basic families, and that there cannot be equilibria of any other type.The third chapter "Optimal Availability of Online Ratings" looks at what role consumer ratings have in determining market outcomes. It shows that more information for buyers does not always lead to increased buyer welfare, and that in some cases it may be preferable to keep some buyers uninformed of existing ratings

All Nash Equilibria of the Multi-Unit Vickrey Auction

This paper completely characterizes the set of Nash equilibria of the Vickrey auction for multiple identical units when buyers have non-increasing marginal valuations and there at least three potential buyers. There are two types of equilibria: In the first class of equilibria there are positive bids below the maximum valuation. In this class, above a threshold value all bidders bid truthfully on all units. One of the bidders bids at the threshold for any unit for which his valuation is below the threshold; the other bidders bid zero in this range. In the second class of equilibria there are as many bids at or above the maximum valuation as there are units. The allocation of these bids is arbitrary across bidders. All the remaining bids equal zero. With any positive reserve price equilibrium becomes unique: Bidders bid truthfully on all units for which their valuation exceeds the reserve price.Vickrey auction; Multi-unit auction; ex-post equilibrium; reserve price; uniqueness

Using ePrognosis to estimate 2-year all-cause mortality in older women with breast cancer: Cancer and Leukemia Group B (CALGB) 49907 and 369901 (Alliance A151503)

Tools to estimate survival, such as ePrognosis (http://eprognosis.ucsf.edu/carey2.php), were developed for general, not cancer, populations. In older patients with breast cancer, accurate overall survival estimates would facilitate discussions about adjuvant therapies