What is a “burkini”?

A “burkini” is not “a cross between a burqa and a swimsuit” (“Ill-suited”, September 3rd). Although the word is a portmanteau of “burqa” and “bikini”, the item itself is not. It is simply a swimsuit, albeit a modest one, and has nothing to do with a burqa. Rather, it is associated with the hijab. A woman who wears the hijab covers her hair and body in public, and so would not show her arms, legs and chest on the beach. Obviously, a substantial portion of Muslim women wear the hijab, whereas only a tiny minority wear a burqa or cover their faces. 

“Burkini” is English and does not come from Arabic. This kind of clothing is referred to natively as maayo muhtashim (modest swimsuit) or malaabis al-bahr al-muhtashim (modest beach clothes). The term “burkini” has started to appear also in Arabic news sources, but the spelling and the fact that it is often written in quotes mark it clearly as a borrowing from English.

KAREN MCNEIL
Revising editor
Oxford Arabic Dictionary
Providence, Rhode Island

Citadel

We certainly won’t argue with your assessment that Citadel has done “spectacularly well” of late (“Law of averages”, August 27th). The analysis by Novus, an analytics firm, of figures from Hedge Fund Research, a data provider, is thought-provoking. The chart you used in the story shows the reversal of fortunes (both positive and negative) for over 900 hedge funds relative to their performance during the 2008 financial crisis. However, the analysis suffers from a material survivorship bias because it does not reflect the performance of the roughly 5,000 hedge funds estimated to have been shuttered (or closed) since 2008.

Citadel’s record in different market environments over the past 25 years speaks for itself. We will continue to focus on delivering investment results that help the sovereign-wealth funds, pension plans, endowments and others who have entrusted us with their capital meet their investment objectives.

ZIA AHMED
Head of media relations
Citadel
Chicago

Colombia and the FARC

You are right that it would be a tragedy if Colombians failed to approve the peace agreement with the FARC guerrillas (“Ending a half-century of war”, August 27th). I first served in Colombia in the late 60s when the FARC were a low-level insurgency but much talked about because of the Cuban Revolution. I returned in the early 90s when they were a much greater threat and peace talks with the ELN had failed in 1991 and again in 1992 and following the 1999-2002 peace process which collapsed so spectacularly.

I share the relief of many Colombians that the FARC have finally agreed to lay down their arms: but also understand the fears of many others who find it hard to believe that the FARC will honour the agreement. Some worry that they will take advantage of the wealth accumulated from drug trafficking, illegal mining, kidnapping and extortion to secure political control of the areas where they have been based and from there possibly mount a popular mobilisation—farmers’ blockades/strikes(paros), industrial action, demonstrations—modelled on president Evo Morales’s successful route to power in Bolivia.

It is also not hard to sympathise with Colombians who find it outrageous that the top leaders of the FARC should face very light non-custodial sentences and be permitted to hold political office immediately despite the crimes against humanity they have committed. International experts on peace processes generally believe that this has been a well managed process and these terms were necessary to secure a deal as the FARC like the IRA had been weakened but not defeated.

Given the strong views on both sides it was a wise decision by president Juan Manuel Santos not to use the powers he has to conclude the deal but to hold a plebiscite, risky as such consultations can be. The agreement is very long and complex and needs to be debated fully. The No campaign in the plebiscite will be led, if not formally, by former president Álvaro Uribe, whose father was killed by the FARC and who himself was their target on several occasions. Ironically it was Mr Uribe’s vigorous campaign against the FARC that convinced them to enter negotiations with his successor.

The implementation of the peace agreement will be a long and difficult task and a Yes vote should open the way for Mr Uribe and other opponents of the deal to contribute to its success by offering, if not support, at least constructive criticism. If this were to happen Colombia’s prospects would indeed be promising.

SIR KEITH MORRIS
British Ambassador to Colombia 1990-94
London

Game theory applications

Your article on John Nash and the prisoner’s dilemma undersold his contribution to understanding social behaviour (“Prison breakthrough”, August 20th). The Nash equilibrium not only describes optimal behaviour in settings such as markets and auctions, but also defines which traits will emerge stably from an evolutionary process.

Nash equilibriums have been used to explain animal behaviours that evolve without any conscious strategy, such as the tendency for many animals to defend territory when they arrive first, or for male peacocks to grow long tails. Humans can arrive at similar behaviours via biological evolution, and also through reinforcement learning or by imitating success, processes that are mathematically similar to biological evolution and lead to similar outcomes.

For example, co-operating in a repeated prisoner’s dilemma can be a Nash equilibrium if players condition their co-operation on others’ past co-operation. People could arrive at this behaviour through conscious deliberation, but also by evolving emotions such as gratitude, or adopting strong norms of reciprocity, precisely what we see in human psychology.

You claimed that when people don’t play in line with a Nash equilibrium in the lab, Nash is not relevant. But when equilibrium behaviour evolves it may not adjust immediately to new circumstances. Peacocks grow long tails even when their mating is determined by zookeepers, and people co-operate in a one-shot prisoner’s dilemma. We would never conclude from captive peacocks that their tails did not evolve as a costly signal to attract mates. We shouldn’t draw the analogous conclusion for human behaviour in unusual contexts.

BETHANY BURUM
MOSHE HOFFMAN
Programme for Evolutionary Dynamics
Harvard University
Cambridge, Massachusetts

You mentioned the role of Nash equilibrium in redesigning the system of matching job offers at hospitals with medical students. Although a common story, the actual history does not line up as the triumph for non-co-operative game theory you think it is. The “deferred acceptance” algorithm now in use in the system was discovered by medical staff before its rediscovery by David Gale and Lloyd Shapley in the 1960s. In any case, it relies on a co-operative game theory of stability, which is an alternative to Nash’s non-co-operative equilibrium, not an application of it.

Nash equilibrium has transformed the way economists think about their field, but clear practical applications of the concept are harder to pinpoint than they might at first appear. The same might be said of Newton’s theory of gravitation and many other great scientific achievements.

E. GLEN WEYL
Senior researcher
Microsoft Research
New York

Demography or bust

When writing about “the global scourge” of parents who have fewer children than they want (“The empty crib”, August 27th) you implied that those who fretted about exploding populations 50 years ago failed to predict the decline of births. In part, because we fretters actually did things to make contraceptives available and to promote smaller families and girls’ education, it is indeed true that birth rates have declined in some poor countries as well as rich ones.

But when a wife, often accepting her husband’s authority, says she wants six children and proceeds to have even more, some fretting is warranted. Childbirth often interrupts a woman’s development and education. Poor parents with large families do not invest in their children’s education, especially for girls.

There appears to be plenty of room for more people in many parts of the world, but opposition to immigration prevents the use of this safety valve. The world faces environmental pressures that have never quite come together as they do today. These interacting problems would be easier to solve without the continued growth of population, especially in areas most sensitive to their effects.

JONATHAN BARON
Professor of psychology
University of Pennsylvania
Philadelphia

Reverend Robert Malthus must surely be turning in his grave at such Pollyannaish assertions as ‘it is not clear that there are too many people’ and ‘population growth…will eventually go into reverse’ (“Wanted”, August 27th). The global human population has doubled to seven billion in just fifty years. Collapsing biodiversity and concerns over fish stocks, land fertility, water security and climate change are all evidence that demand is exceeding supply. If population growth does reverse, the UN thinks it will not be until there are at least four billion more people.
Your leader asserts that couples who have fewer children than they desire suffer ‘anguish’, ‘sorrow’, depression’ and even ’social catastrophe’. Well, boo-hoo. Greed and growth are not admirable or indeed sustainable in a crowded, finite planet. If such couples substituted social concern for self-centeredness, they might be more content.

SIMON ROSS
Chief Executive
Population Matters
London

What a trilemma!

Regarding the origins of the Mundell-Fleming trilemma in international economics (“Two out of three ain’t bad”, August 27th), John Maynard Keynes referred to the dilemma of choosing between internal price stability and external exchange-rate stability in his “A Tract on Monetary Reform”, published in 1923. In a 1950 draft of his famous essay “The Case for Flexible Exchange Rates”, Milton Friedman said that, with the introduction of exchange controls in the 1930s, Keynes’s dilemma “has become a trilemma: fixed exchange-rates, stable internal prices, unrestricted multilateral trade; of this trio, any pair is attainable; all three are not simultaneously attainable.”

As early as 1948, Friedman had been discussing this point in his lectures at the University of Chicago. In a letter to The Economist (January 3rd 1953), he took you to task for ruling out flexible exchange rates as a cure for the dollar shortage, accusing you of perpetuating “mercantilist fallacies” dressed up in “egalitarian jargon”. Apparently The Economist of the day preferred to resolve the trilemma by maintaining exchange controls and fixed exchange-rates rather than choosing free trade and monetary-policy autonomy. Who do you now think had the better of that argument?

DOUGLAS IRWIN
Dartmouth College
Hanover, New Hampshire

Editor’s note: The letter from Milton Friedman can be found at: www.economist.com/friedmanletter

They boldly went

A leader and lengthy article on the exciting discovery of a new planet, and all that entails for space travel (“Brave new worlds”, “Proximate goals”, August 27th). But no reference to the 50th anniversary of the first episode of “Star Trek”?

For shame.

RICHARD ROBINSON
Los Alamos, New Mexico