Thursday, September 8, 2011

Instructions are part of a market's design

Whenever my colleagues and I help design a new marketplace, we're very aware that a part of the market mechanism are the instructions that accompany it. There's no reason to assume that the benefits of a strategy-proof mechanism, for example, will be realized if the participants aren't made fully aware that it is strategy-proof, so that it is safe for them to reveal their true preferences.

That is why I was glad when the HBS MBA program invited me to explain the modified serial dictatorship mechanism that Clayton Featherstone and I designed for the first year of operation of a 2nd year MBA field experience module, in which Harvard MBA students will choose countries in which to spend time at a company.  (We felt it was particularly important to start with a strategy-proof mechanism, for reasons we hope to write about in the not too distant future.)  Here's the video of my explanation (which can also be found at http://video.hbs.edu/videotools/play?clip=aroth_field2_algorithm or, if that is gated, http://stream.hbs.edu/remediated/cd/aroth_field2_algorithm.mp4)




While I think of it, let me mention that Clayton is an unusually talented and versatile market designer, theorist and experimenter who will be on the econ job market this year.

Wednesday, September 7, 2011

School choice around the U.S.: some short video interviews

Northwestern's journalism school has a project on school choice that allows you to click on a map of the U.S. and see very short (1 minute) clips of video interviews they did about school choice in the indicated cities:
 One size does not fit all

You can glimpse my filing system for journals in the background of interviews they did with me and Neil Dorosin of IIPSC about Boston, New York, and Denver...

Tuesday, September 6, 2011

Mechanism design conference: Copenhagen, Sept. 6-9.

WORKSHOP: NEW TRENDS IN MECHANISM DESIGN, Sept 6-9, 2011.

"A main focus of the workshop will be contributions from computer science to the field of mechanism design."

Keynote Speakers:

Monday, September 5, 2011

Repugnant markets involving altruistic motivations

Kim Krawiec follows up on Kieran Healy's work on markets for organs, and how the distinction between gift giving and buying and selling isn't so clear.

Krawiec writes (I quote at length, but not the whole thing):

"...I agree with Kieran that financial incentives for human organs are more likely to win social acceptance if they resemble the gift-based allocation systems that have already gained social legitimacy. And the oocyte market – a clearly market-based system with the trappings of gift, including the language of donation -- is a good example of this phenomenon. 

In fact, as I’ve discussed before, this disconnect between market realities and gift narrative is an important feature of many taboo trades.  By normalizing otherwise jarring transactions, gift narratives may facilitate markets that otherwise would stagnate under the weight of social disapproval. For those, like me, who believe there is social value in enabling the infertile to reproduce or those dying from kidney failure to live – and, by corollary, allowing those who consider themselves better off by the receipt of compensation in exchange for an egg or kidney – to do so, this is a good thing. 
At the same time, though, the oocyte market example also illustrates the costs of denying market realities in favor of the pretense of gift exchange -- gifts in name only: 
(1) Legal misfit
Gift-based exchange regimes are typically governed by a different set of legal rules than are market-based exchange regimes.  We tend to recognize, for example, the possibilities for opposing interests and opportunistic behavior in a regime of market-based exchange.  And many legal rules governing market-based regimes are designed with these considerations in mind. In contrast, we often assume (incorrectly, especially when the gift is one in name only) an absence of opportunism and an alignment of interests in the case of gift-based exchange. 
(2) Social stereotypes
I do not know if, or how, this would play out in organ markets, but it has for some time concerned me with respect to reproductive markets, especially the oocyte and surrogacy markets.  Scholars have long noted the presumption that many services provided by women, including reproductive and domestic labor, should be provided altruistically, despite their high economic value.  Says Mary Anne Case, for example:
Much of what women have market power over, such as their sexual and reproductive services, they have long been expected not to commodify at all. Even when monetary compensation is allowed, it is often kept low and female providers are expected to be interested in rewards other than money.
The continued insistence that egg donors are, and should be, motivated primarily by altruism and the desire to help others, rather than by the desire for monetary compensation, threatens to reinforce gendered notions that the market activities of women are driven in large part by altruism and that women as a group are uninterested in reaping the full gains of trade from the provision of their goods and services. 
The comparison to sperm markets is especially telling. The insistence on the altruistic motivations of egg donors is in stark contrast to the presumed motivations of sperm donors, who are recruited through materials that ask, “Why not get paid for it?” and advertise, “your sperm can earn!” 
...
In the end, gifts in name only represent a trade-off.  On the one hand, the language of donation coupled with the realities of market-based exchange has the capacity to legitimate otherwise troubling exchanges, facilitating life-saving operations and parenthood for the infertile.  At the same time, gift-in-name-only exchange has consequences for the social, legal, and market structure of these industries, and for the consumers, producers, and others, including the public-at-large, affected by them."

Sunday, September 4, 2011

Call for papers: NBER market design conference, October 28-29, 2011

Susan Athey and Parag Pathak have circulated the following call for papers.


From: Susan Athey and Parag Pathak
To: NBER Market Design Working Group

The National Bureau of Economic Research workshop on Market Design is a forum to discuss new academic research related to the design of market institutions, broadly defined. The next meeting will be held in Cambridge, Massachusetts, on Friday and Saturday, October 28-29, 2011.

We welcome new and interesting research, and are happy to see papers from a variety of fields. Participants in the past meeting covered a range of topics and methodological approaches.  Last year's program can be viewed at:  http://www.nber.org/~confer/2010/MDf10/MDf10prg.html

The conference does not publish proceedings or issue NBER working papers - most of the presented papers are presumed to be published later in journals.

There is no requirement to be an NBER-affiliated researcher to participate.  Younger researchers are especially encouraged to submit papers.  If you are interested in presenting a paper this year, please upload a PDF version by September 9, 2011 to this link:

Preference will be given to papers for which at least a preliminary draft is ready by the time of submission. Only authors of accepted papers will be contacted.

For presenters and discussants in North America, the NBER will cover the travel and hotel costs. For speakers from outside North America, while the NBER will not be able to cover the airfare, it can provide support for hotel accommodation.

There are a limited number of spaces available for graduate students to attend to conference, though we cannot cover their costs. Please email ppathak@mit.edu a short nominating paragraph.

Please forward this announcement to any potentially interested scholars.  We look forward to hearing from you.

Saturday, September 3, 2011

Dating sites for French farmers

If a dating site specializing in French farmers sounds specialized to you, consider the special problems of farmers: they are unusually immobile, as their work is typically tied to a specific plot of land, and they don't meet many potential marriage partners in the course of a typical work day.  So their problem combines those that have given rise to other kinds of specialized dating sites that make a thick market for e.g. particular ethnic groups or people with disabilities, as well as location and career choice.

The NY Times has a nice article by MAÏA de la BAUME covering several such sites: With Help Online, French Farmers Now Playing the Field

"The lack of love in the countryside is a serious topic for a country that sees its bedrock in small farmers and their produce, which is supposed to be uniquely of the place where it is grown. According to the Agriculture Ministry, about 30 percent of male French farmers did not have a partner in 2009."

Friday, September 2, 2011

Signaling in Internet Dating Markets (and welcoming Soo Lee to Harvard)

 Soohyung Lee arrived today at Harvard where she'll spend the coming academic year as a research visitor, on leave from the University of Maryland. (She'll be sitting in Baker Library, come by and join us for coffee some morning and say hello.)

Here's a recent paper that I admire:
Propose with a Rose? Signaling in Internet Dating Markets, (ungated version here)
by Soohyung Lee, Muriel Niederle, Hye-Rim Kim, Woo-Keum Kim
NBER Working Paper No. 17340
August 2011

"Abstract: The large literature on costly signaling and the somewhat scant literature on preference signaling had varying success in showing the effectiveness of signals. We use a field experiment to show that even when everyone can send a signal, signals are free and the only costs are opportunity costs, sending a signal increases the chances of success. In an online dating experiment, participants can attach “virtual roses” to a proposal to signal special interest in another participant. We find that attaching a rose to an offer substantially increases the chance of acceptance. This effect is driven by an increase in the acceptance rate when the offer is made to a participant who is less desirable than the proposer. Furthermore, participants endowed with more roses have more of their offers accepted than their counterparts."

One of the things I like about this paper (aside from the fact that it reports an experiment in market design, that is), is that it also sheds some light on the signaling mechanism for new Ph.D.s on the economics job market.

Thursday, September 1, 2011

First class tomorrow morning: slides on website

For students in our market design class which starts tomorrow, some material for the first lecture is on the course website...http://isites.harvard.edu/icb/icb.do?keyword=k80599&pageid=icb.page425742 .

From now on I won't announce course material on the blog...keep an eye on the course website for that.

See you tomorrow morning.

Theory of privacy

Several courses are being offered that deal with new theories of data privacy, concerning how to usefully answer queries from a database while preserving the privacy of individuals in the database, even if the queries can be combined with auxiliary information from other data sources.

These concerns arise in response to the practical observation that even "anonymized" databases can often be "de-anonymized" by combining them with other information.

All the course sites below link to papers in the literature, and, at least at this early stage of development, there seems to be a great deal of consensus on which papers to cover.

The Algorithmic Foundations of Data Privacy taught by Aaron Roth this Fall at Penn

Algorithmic Challenges in Data Privacy taught at Penn State by Sofya Raskhodnikova and Adam D. Smith

Foundations of Privacy taught at Weizmann by Moni Naor.

Wednesday, August 31, 2011

Multiple publication and plagiarism in economics journals

An unusual insight into the culture of academic publication comes in a recently published letter from David Autor, the editor of the Journal of Economic Perspectives to a famous economist who published an article there that was substantively identical to papers he had published elsewhere.

David Autor writes:
"...There is a very substantial overlap between these articles and your JEP publication. Indeed, to my eye, they are substantively identical. Based on discussions with the editors of these journals, we have confirmed that the JEBO article was in press and the R&S article under review while your article was under revision for JEP. At the time we accepted your paper for JEP, we could not readily have learned of these two overlapping articles since they were at the time unpublished. Further obscuring the links among these articles is the fact that none of your four articles cites any of the other three. Had you chosen to inform us of the JEBO and R&S articles prior to the publication of your JEP article, we would of course have no grounds for complaint. In that case, however, we would not have published your article.

"We view your publication of this substantive material in multiple journals simultaneously as a violation of the spirit of the editorial agreement with American Economic Association that you signed in the winter of 2010, which states "The Author(s) warrant(s) that the above-named manuscript is his or her own original work of authorship and has not been published previously." The AEA does not intend to pursue legal action against you for violation of copyright. However, we find your conduct in this matter ethically dubious and disrespectful to the American Economic Association, the Journal of Economic Perspectives and the JEP's readers..."

The letter from Autor is followed by a letter of apology from the senior author of the papers in question, Zurich's Professor Bruno Frey.
"...It was a grave mistake on our part for which we deeply apologize..."
**********

RePEc maintains a plagiarism page on which it includes links to offending authors and some of the case material, including the present case.

Tuesday, August 30, 2011

More on the taking of photos

Here are two followups on my earlier post today on British Airways' claims about photographs. The first via Paola Manzini, concerns US Airways' similar claims. The second, via Ben Edelman, concerns a very recent court victory in the U.S. by the ACLU, regarding citizens' rights to photograph police officers.

Woman thrown off U.S. Airways flight for taking a picture of rude air steward's name tag.
"A photographer was thrown off a U.S. Airways flight and branded a security risk after she took a photo of a rude air steward's name tag so she could complain about her."


A Victory for Recording in Public!
"The CMLP is thrilled to report that in the case of Glik v. Cunniffe, which the CMLP has blogged previously and in which the CMLP attempted to file an amicus brief, the U.S. Court of Appeals for the First Circuit has issued a resounding and unanimous opinion in support of the First Amendment right to record the actions of police in public."

British Airways Conditions of Carriage

A disturbing incident at British Airways raises interesting questions about their Conditions of Carriage, the fine-print online contract that you and they enter into when you buy a ticket. (In many markets what is bought and sold is at least partly a legal contract.)

To make a long story short, we were accosted in the public (pre-security) area of London's Heathrow airport by a bizarrely aggressive BA employee who declined to identify himself. I took his picture. When I was about to board the plane an hour and a half later, I was asked to step aside, where another BA employee told me that photographing BA employees was forbidden, and it was a condition of carriage that I delete the photo.

I have not been able to find that clause in the published COC, and have written to BA for clarification.

Monday, August 29, 2011

Conference on Frontiers in Market Design

Bettina Klaus has announced two conferences on market design. The one that is imminent is


Market Design Workshop on September 14th, 2011, Maastricht University, The Netherlands:
The speakers are Bettina KlausFlip KlijnScott Duke KominersMorimitsu KurinoAlexey KushnirMarkus Walzl, and Alexander Westkamp. The workshop program and abstracts of presented papers can be downloaded here:Workshop Program and Abstracts of Presented Papers

And here's a "pre-announcement" of one in May...

Frontiers in Market Design: Matching Markets
May 20 – 23, 2012
Centro Stefano Franscini (http://www.csf.ethz.ch/), MonteVerità, CH

"Dear colleagues,


Together with Itai Ashlagi, Péter Biró, Federico Echenique, Flip Klijn, and Alvin Roth, I am planning a conference on Market Design with a focus on Matching Markets at a very nicely located Swiss conference centre.


We aim to organize a worthy follow-up to the conference that celebrated the 20th anniversary of Two-Sided Matching: A Study in Game-Theoretic Modeling and Analysis by Alvin Roth and Marilda Sotomayor (http://econ.duke.edu/erid/conferences/roth-and-sotomayor-twenty-years-after). We hope to bring together researchers from different fields (economics, computer science, etc.) and attract many young researchers.


With this pre-announcement, we would like to see how many participants we might be able to count on (we will be able to accommodate up to 22 talks). The reason for this unorthodox procedure is that I will have to make a reservation of the conference room and of the needed accommodation capacity at the Conference Centre hotel well in advance (with penalties applying if the reserved capacities are left unused).


Depending on the exact number of participants, the conference fee will amount to about 800 CHF (this conference fee includes the accommodation for 3 nights at Hotel Monte Verità and full board during the conference). Unfortunately, this currently amounts to almost 1000$ (the Swiss Franc is quite strong). We did not yet succeed in obtaining further funding for the conference that would allow us to subsidize the on-site costs), but we are still working on that. If you can think of any funding opportunity we might be able to apply for, please let me know.


In order for us to facilitate the conference planning and later also reserve the corresponding conference room and conference accommodation, I would like to ask you to send an e-mail to me (Bettina Klaus at econlausanne@yahoo.com) before October 1st indicating the following:


(A) You are very likely to attend this conference (this would be an indication for me to count you as a participant of the conference for the conference room and accommodation reservation).


(B) You are very interested in attending this conference, but not sure yet (I can then keep you informed via a conference mailing list).


(C) You are not likely to attend the conference. In this case, no need to send an e-mail (you will not receive further mailings concerning the conference).


Thanks a lot & have a great (remaining) summer,
Bettina et al."

Sunday, August 28, 2011

Transplant organs from executed prisoners

In another sign of what constitutes a repugnant transaction, the American Journal of Transplantation now has this notice on its "Instructions to Authors" page:

"New Policy Effective May 2011
AJT will not accept manuscripts whose data derives from transplants involving organs obtained from executed prisoners. Manuscripts writing about this practice (e.g. an editorial or a report recounting the secondary consequences of this practice) may be considered at the discretion of the Editorial Board, but require a written appeal to the Board prior to submission of the manuscript."

Saturday, August 27, 2011

Breast milk

The barriers to sale of human breast milk seem to be falling. Duncan Gilchrist points me to this article in Wired: Liquid Gold: The Booming Market for Human Breast Milk, which reports a booming private market, at high prices.

"Most body fluids, tissues, and organs—semen, blood, livers, kidneys—are highly regulated by government authorities. But not breast milk. It’s considered a food, so it’s legal to swap, buy, or sell it nearly everywhere in the US. This accounts, in part, for the widely varying quality and safety standards in the online market for milk. For their part, Prolacta and nonprofit milk banks have rigorous screening processes for potential donors, including tests for drugs, hepatitis, and HIV. But Only the Breast and the volunteer sites, which see themselves more as communities than commodity markets, don’t screen donors or assume responsibility for the milk they help disseminate."

Friday, August 26, 2011

Market design courses in Boston this semester

Boston is humming with market design courses.

Tayfun Sonmez will be offering an undergraduate course on market design at Boston College: Advanced Microeconomic Theory (T Th 13:30 - 14:45 AM).
There's no web site, but the course focuses on various aspects of matching, including some of Tayfun's latest work.

Susan Athey will be offering an undergrad course on market design at Harvard:
Economics 1056: Market Design Harvard College/GSAS: 69207 Fall 2011-2012   Location: Sever Hall 106, Meeting Time: Tu., Th., 2:30-4

Ben Edelman and Peter Coles will be offering an MBA course at HBS,

Intended primarily for MBA’s.  Has one module firmly grounded in market design: 
“Monetization and Market Design: What structures, rules, and incentives create a well-functioning online ecosystem? We examine review and reputation systems, dynamic marketplace pricing, and institutions to create a safe environment for users, while at the same time protecting a site from liability.”


Peter Coles and I will be giving a graduate course on market design at Harvard:
Economics 2056a: Market Design  Harvard College/GSAS: 3634, Fall 2011-2012, Location: Littauer Center M-16, Meeting Time: F., 9-12

And next semester, Parag Pathak will be offering an undergrad course in market design at MIT.

Update: and Sven Seuken points out that David Parkes at Harvard is offering "Economics and Computation" in Computer Science this Fall. It will touch on a couple of market design topics: http://www.seas.harvard.edu/courses/cs186/

Thursday, August 25, 2011

School choice in New York City

Thomas Toch and Neil Dorosin write about New York City high school choice in Education Week: NYC Program Means Real Public School Choice for Students

"New York’s ambitious high school selection system isn’t perfect. But it has liberated thousands of students from failing neighborhood high schools, transformed the city’s high school principals from bureaucrats to entrepreneurs, improved the perception of public schools among middle-class families...
...
"Of the small number of cities that permit students to select their public schools, most make school choice optional and relatively few families participate. New York City has taken the bold step of requiring rising 9th graders to select their high schools, a strategy that has created a far more vibrant public school marketplace than exists anywhere else in the country. "
*********

(And here's our latest paper on that...
Abdulkadiroglu, Atila, Parag A. Pathak, and Alvin E. Roth, "Strategy-proofness versus Efficiency in Matching with Indifferences: Redesigning the NYC High School Match,'' American Economic Review, 99, 5, Dec. 2009, pp1954-1978.)

Wednesday, August 24, 2011

Poker refugees

April 15, 2011 has come to be known as Black Friday by online poker players in the U.S. On that day, indictments were issued against major offshore sites, PokerStars, Full Tilt Poker and Absolute Poker, for violating U.S. anti-gambling laws. An unknown but nontrivial number of Americans had made their living playing on those sites. Now, if they wish to continue playing, they must do so from overseas.

Consequently, a new class of migrant workers has developed, and a service has grown up to help them relocate: Poker refugees.

Here's a story about it: US poker players turned into refugees by online gaming ban

"American card players are hardly a high priority for humanitarian organisations protecting the rights of the world's imperilled communities. But such is the current plight of professional poker players in the United States, where online poker has been all but illegal since April, that a new service launched last week offering to relocate beleaguered card players to "poker-friendly countries" around the world.

"The service, called Poker Refugees, was launched in response to the US Department of Justice's clampdown on online poker operators earlier this year, which effectively enforced prohibition on online poker in the US. On what has become known in the industry as "Black Friday", the three biggest poker sites in the world were closed to US traffic and their executives indicted by the FBI on numerous charges, including money laundering and bank fraud.

"The operators have since either ceased trading or closed their doors to American customers, leaving thousands of professional players without income unless they dramatically change their circumstances.

"They're not moving outside of the US because they want to go on vacation, or because they want to pay less taxes," said Kristin Wilson, a real-estate agent based in Costa Rica, and a partner in Poker Refugees. "They're moving because they have to keep their job, keep their career and support their families."

Tuesday, August 23, 2011

Child marriage

Child marriage by very young children is under discussion again in Saudi Arabia, the Wall Street Journal reports. Part of the issue is just how young should count as young: Cleric Fights Saudi Bid to Ban Child Marriages

"RIYADH, Saudi Arabia—A senior Saudi cleric issued a religious ruling to allow fathers to arrange marriages for their daughters "even if they are in the cradle," setting up a confrontation between government reformers and influential conservative clergy.

"Sheik Saleh al-Fawzan, one of the country's most important clerics, issued the ruling after the Justice Ministry said this month it would act to regulate marriages between prepubescent girls and men in the Islamic kingdom.
...
"The fatwa marks the second time in a year that religious authorities have knocked back a government initiative to move forward on social issues involving women.

"Last year, King Abdullah bin Abdelaziz al-Saud pushed for higher female employment, suggesting that women ought to be allowed to work as supermarket cashiers, only for the job to be ruled off-limits to the gender by the Grand Mufti, the country's highest religious leader.

"In the conservative Islamic kingdom, women aren't allowed to drive and can't work, travel abroad or undergo surgery without the permission of a male relative.
...
"Saudi media reported that the Justice Ministry would push ahead with setting a minimum age for marriage, despite the fatwa. The ministry couldn't be reached to comment for this article.

"In recent months, a spate of stories about young Saudi girls being forced by their fathers to marry middle-age men for lavish dowries or other personal gains has prompted editorials in local media denouncing the practice and calling for change.

"In April, the English-language Arab News reported that a court granted a 12-year-old girl a rare divorce from her 80-year-old husband, who had paid her father a dowry of 85,000 Saudi riyals, or $23,000.
...
""Scholars have agreed that it was permissible for fathers to marry off their young daughters, even if they are in the cradle," Sheik Fawzan wrote in his fatwa. "But it isn't permissible for their husbands to have sex with them unless they are capable of being placed beneath and bearing the weight of the men."

"He cited the example of the prophet's wife Aisha, who he said was wed at the age of six, but didn't have sex until she was nine.

"Saudi Arabia's Grand Mufti said in 2009 that it was acceptable for girls aged 10 and above to marry."

Monday, August 22, 2011

Marriage supply and demand, and equilibrium behavior

Two recent posts caught my eye. The first, by Robert Frank in the NY Times, speculates on how the baby boom may have changed sexual mores in the U.S., and reports on a recent article about the imbalance of men and women in China and the behavioral changes this may be causing: Supply, Demand and Marriage .

The second, by Ralph Richard Banks in the WSJ, speaks about the marriage behavior of black men and women in the U.S., and relates it to the reluctance of black women to marry non-black men, and their resulting shortage of marriage partners: An Interracial Fix for Black Marriage

Here's Frank:
"In the United States, the end of World War II and the return of millions of troops set off the baby boom. In the second half of the 1940s, the population swelled by almost 14 percent, versus growth of less than half of 1 percent during the first half of the decade. By the mid-1960s, many of those babies were reaching the traditional marriage age.

"At the time, it was American custom for women to marry men several years older than themselves. In a typical wedding in 1969, for example, the bride might have been born in 1947 and the groom in 1943. Because of that custom, women at the leading edge of the baby boom confronted a significant shortfall of potential marriage partners.
...
""Before the 1960s, cultural norms encouraged celibacy before marriage. The breakdown of those norms has been widely attributed to the introduction of oral contraception...
"The supply-and-demand model bolsters the skeptics’ concerns. ... The sexual revolution, which bent cultural norms toward male preferences, may thus be partly explained by the excess demand for grooms in the 1960s."

And here's Banks:
"Nearly 70% of black women are unmarried, and the racial gap in marriage spans the socioeconomic spectrum, from the urban poor to well-off suburban professionals. Three in 10 college-educated black women haven't married by age 40; their white peers are less than half as likely to have remained unwed.

"What explains this marriage gap? As a black man, my interest in the issue is more than academic.
...
"Black women confront the worst relationship market of any group because of economic and cultural forces that are not of their own making; and they have needlessly worsened their situation by limiting themselves to black men. I also arrived at a startling conclusion: Black women can best promote black marriage by opening themselves to relationships with men of other races.
...
"Part of the problem is incarceration. More than two million men are now imprisoned in the U.S., and roughly 40% of them are African-American. At any given time, more than 10% of black men in their 20s or 30s—prime marrying ages—are in jail or prison.
Educationally, black men also lag. There are roughly 1.4 million black women now in college, compared to just 900,000 black men. By graduation, black women outnumber men 2-to-1. Among graduate-school students, in 2008 there were 125,000 African-American women but only 58,000 African-American men. That same year, black women received more than three out of every five law or medical degrees awarded to African-Americans.

"These problems translate into dimmer economic prospects for black men, and the less a man earns, the less likely he is to marry. That's how the relationship market operates. Marriage is a matter of love and commitment, but it is also an exchange. A black man without a job or the likelihood of landing one cannot offer a woman enough to make that exchange worthwhile.

"But poor black men are not the only ones who don't marry. At every income level, black men are less likely to marry than are their white counterparts. And the marriage gap is wider among men who earn more than $100,000 a year than among men who earn, say, $50,000 or $60,000 a year.

"The dynamics of the relationship market offer one explanation for this pattern. Because black men are in short supply, their options are better than those of black women. A desirable black man who ends a relationship with one woman will find many others waiting; that's not so for black women."

HT: Sangram Kadam