Essa dos nomes seria legal realmente

Co-autor de Freakonomics promete lançar novo livro

O segundo volume terá capítulos sobre a economia da prostituição e a relação de macacos e o dinheiro

EXAME Stephen J. Dubner, o jornalista do New York Times co-autor do livro Freakonomics, um dos maiores sucessos da literatura econômica desta década, afirmou hoje que vai lançar um novo volume do livro em que deve tratar de assuntos como a economia por trás da prostituição e experiências de macacos com dinheiro. Dubner e o professor de Economia da universidade de Chicago Steven D. Levitt lançaram em 2005 o best-seller Freakonomics. Teorias como a da correlação entre a legalização do aborto e a posterior redução da criminalidade nos Estados Unidos correram o mundo e fizeram com que o livro chegasse ao segundo lugar na lista de mais vendidos do New York Times.

Durante uma conferência sobre gerenciamento de dados em Boston (Massachusetts), ele afirmou que um dos capítulos do novo livro tratará sobre os efeitos psicológicos do dinheiro entre macacos. Em um laboratório de New Haven (Connecticut), os animais foram treinados pelo economista da universidade de Yale Keith Chen a ganhar argolas que representavam dinheiro e poderiam ser trocados por doces e alimentos. Ele descobriu que os macacos agem como os humanos na tentativa de juntar o máximo de recursos e fazer seu melhor uso.

Chen também desenvolveu duas formas de fazer os macacos experimentarem a sensação de ganhar e perder dinheiro. A conclusão de que eles mostraram uma preferência irracional pela sensação de ganho foi a mesma do que a encontrada em outro estudo sobre "day traders" (pessoas que fazem negociações de curto prazo na bolsa) e fez o próprio Chen se questionar até que ponto o conhecimento do comportamento dos macacos pode ser útil para ajudar a entender a própria raça humana.

Em determinado momento, Chen também observou que um macaco deu uma argola para outro. Em seguida, os dois macacos começaram a fazer sexo. E depois o macaco que recebeu a argola foi até o pesquisador para trocá-la por comida, afirmou Budner. "Freakonomics mostra como o mundo realmente é. Você não pode mudar o mundo se não entender como ele funciona", afirmou Dubner, segundo o site de tecnologia CNET.com.

um macaco deu uma argola para outro. Em seguida, os dois macacos começaram a fazer sexo.

bixo, eu num faço séquisso com quem me dá dinheiro não...

Ô Jr, pra esse assunto eu acredito em design inteligente , num descendo do macaco não...

Atrasado, como sempre, acabei de ler o livro, mais na empolgação do "mês economia" (tinha lido o "Undercover Economist", do Tim Harford). Curti mais o primeiro, que fala mais de economia "per se", mas o Freakonomics é bem legal também. Fazendo uma busca do cara, vi a página dele, e inclusive um curso que ele dá com (quase) toda a bibliografia available, "Introduction To Doing Empirical Research (Econ 421)". Talvez interesse para alguém.

http://pricetheory.uchicago.edu/levitt/econ421.html



Maldito seja o Mends, que vai espalhando a idéia de que economia pode ser legal também

Estava lendo o livro, que por ser uma edição mais nova tem uns posts do blog dele. Por isso, vi que tem uma resposta ao artigo que o Mends cita a'i em cima, de modo que resolvi incluir aqui.

O post com os links está em http://www.freakonomics.com/blog/2005/12/05/back-to-the-drawing-board-for-our-latest-criticsand-also-the-wall-street-journal-and-oops-the-economist/
Back to the drawing board for our latest critics…and also the Wall Street Journal and (Oops!) the Economist.

Thanks to articles in the Wall Street Journal and the Economist, a working paper by Chris Foote and Chris Goetz that is sharply critical of John Donohue and me has gotten an enormous amount of attention.

In that working paper Foote and Goetz criticized the analysis underlying one of the tables in our original article that suggested a link between legalized abortion and crime. (It is worth remembering that the approach they criticize was one of four distinct pieces of evidence we presented in that paper…they offer no criticisms of the other three approaches.)

Foote and Goetz made two basic changes to the original analysis we did. First, they correctly noted that the text of our article stated that we had included state-year interactions in our regression specifications, when indeed the table that got published did not include these state-year interactions. Second, they correctly argue that without controlling for changes in cohort size, the original analysis we performed provided a test of whether cohorts exposed to high rates of legalized abortion did less crime, but did not directly afford a test of whether “unwantedness” was one of the channels through which this crime reduction operated. (Note: we didn’t claim that this particular analysis was a direct test of the “unwantedness” hypothesis. This last section of the paper was the most speculative of analysis of all that we did and frankly we were surprised it worked at all given the great demands it put on the data.) They found that once you made those changes, the results in our original Table 7 essentially disappear.

There is, however, a fundamental problem with the Foote and Goetz analysis. The abortion data that are available are likely to be quite noisy. As one adds more and more control variables (e.g. nearly 1,000 individual state-year interactions), the meaningful variation in abortion rates gets eaten away. The signal-to-noise ratio in what remains of the variation in measured abortions gets worse and worse. That will lead the measured impact of abortions on crime to dwindle. Because the analysis is carried out with a unit of analysis of a state-year-single year of age, the analyses performed are highly saturated with interactions: state-age interactions, age-year interactions, and state-year interactions. Together, these interactions account for over 99% of the variance in arrest rates and over 96% of the variation in the abortion proxy. It is an exercise which is incredibly demanding of the data.

In light of this, it seems uncontroversial that one would want to do the best one could in measuring abortion when carrying out such an exercise.

The abortion measure used by Foote and Goetz is one that is produced by the Alan Gutmacher Institute. The Alan Gutmacher Institute makes estimates based on surveys of abortion providers of the number of abortions performed per live birth in each state and year.

To proxy for the abortion exposure of, say, 19 year olds arrested in California in 1993, Foote and Goetz use the abortion rate in California in 1973. This is not an unreasonable first approximation (and indeed is the one we used in most parts of our original paper because it is simple and transparent), but it is just an approximation for a number of reasons:

1) There is a great deal of cross-state mobility. So many of the 19 year olds arrested in California in 1993 were not born in California. They were born in other states, or possibly other countries. Indeeed, I believe that recent figures suggest that over 30% of those in their late teens do not reside in the state in which they were born.

2) Using a date of 20 years earlier to proxy for the abortion exposure of a 19 year old induces an enormous amount of noise. If I am a 19 year old sometime in 1993, I may have been born as early as Jan. 2, 1973 (that would make me still 19 on Jan. 1, 1993) or as late as Dec. 31, 1974 (that would have me turning 19 on Dec. 31, 1993). Abortions occur sometime in advance of birthdays, typically about 13 weeks into a pregnancy. So the relevant date (roughly) of when those who are 19 in 1993 would have been exposed to legalized abortion is about six months before they were born, or July 2, 1972-June 30, 1974. While that window overlaps with the year 1973 (which is what Foote and Goetz use as their time period of abortion exposure), note that it also includes half of 1972 and half of 1974!

3) A non-trivial fraction of abortions performed in the United States, especially in the time when legalization was taking place, involved women crossing state lines to get an abortion. As a consequence, measuring abortions in terms of the state in which the abortion is performed (which is what the data Foote and Goetz use does), rather than the state of residence of the woman getting the abortion, induces further measurement error into their abortion proxy.

4) The Alan Gutmacher abortion numbers are, even by the admission of the people who collect the data themselves, far from perfect. Indeed, the correlation between these abortion estimates and another time series collected by the CDC is well below one, suggesting that even if problems (1)-(3) did not exist, there would be substantial measurement error. The correlation between the Alan Gutmacher measure and the CDC measure, not surprisingly, gets lower and lower the more control variables that are included. This is exactly what one would expect if the controls are taking the signal out of the abortion measures and leaving behind mostly noise.

What John Donohue and I have done (with fantastic research assistance from Ethan Lieber), is attempted to address as best we can these four problems with the abortion measure that Foote and Goetz are using. In particular, we do the following:

1) As we describe in our original paper on abortion, one can deal with cross-state mobility by using the decennial censuses to determine the state of birth for the current residents of a state (the results from carrying out this correction in our crime regressions are reported in Table 5 of the original 1999 paper). This is possible to do because the census micro data reports the state of birth and current state of residence for a 5% sample of the U.S. population. Note that the correction we are able to make is unlikely to be perfect, so it may not fully solve the problem, but it clearly moves us in the right direction.

2) Given that the window of abortion exposure that 19 year olds in 1993 spans from 1972 to 1974, the obvious solution to this problem is to allow abortions performed in 1972, 1973, and 1974 to influence arrests of 19 year olds in 1993. It is straightforward to work out roughly the weights that one wants to put on the different years’ abortion rates (or one can do it non-parametrically and let the data decide — the answers are virtually identical).

3) In order to deal with the fact that many women were crossing state lines to get abortions in the 1970s, we use the Alan Gutmacher Institute’s estimates of abortions performed on women residing in a state relative to live births in that state. (We were unaware of the existence of these better data when we wrote the initial paper, otherwise we would have used them at that time.) There is little question that measuring abortions by state of residence is superior to measuring them by where the procedure is performed.

4) The standard solution to measurement error is to perform instrumental variables in which one uses one noisy proxy of the phenomenon that is poorly measured as an instrument for another noisy proxy. (I recognize that most readers of this blog will not understand what I mean by this.) In this setting, the CDC’s independently generated measure of legalized abortions is likely to be an excellent instrument. Because there is so much noise in each of the measures, the standard errors increase when doing this IV procedure, but under a standard set of assumptions, the estimates obtained will be purged of the attentuation bias that will be present due to measurement error.

I think that just about any empirical economist would tend to believe that each of these four corrections we make to the abortion measure will lead us closer to capturing a true impact of legalized abortion on crime. So, the question becomes, what happens when we replicate the specifications reported in Foote and Goetz, but with this improved abortion proxy?

The results are summarized in this table, which has two panels. The top panel are the results for violent crime. The bottom panel corresponds to property crime.

Starting with the first panel, the top row reports the same specifications as Foote and Goetz (I don’t bother showing their estimates excluding state-age interactions because it makes no sense to exclude these and they themselves say that their preferred specifications include state-age interactions). We are able to replicate their results. As can be seen, the coefficients shrink as one adds state-year interactions and population controls.

The second row of the table presents the coefficients one obtains with our more thoughtfully constructed abortion measure (changes 1-3 above having been made to their abortion measure). With a better measure of abortion, as expected, all the estimated abortion impacts increase across the board. The results are now statistically significant in all of the Foote and Goetz specifications. Even in the final, most demanding specification, the magnitude of the coefficient is about the same as in the original results we published that didn’t control for state-year interactions or population. The only difference between
what Foote and Goetz did and what we report in row 2 is that we have done a better job of really measuring abortion. Everything else is identical.

The third row of the table reports the results of instrumental variables estimates using the CDC abortion measure as an instrument for our (more thoughtfully constructed) Alan Gutmacher proxy of abortions. The results all get a little bigger, but are more imprecisely estimated.

The bottom panel of the table shows results for property crime. Moving from Foote and Goetz’s abortion measure in the top row to our more careful one in the second row (leaving everything else the same), the coefficients become more negative in 3 of the 4 specifications. Doing the instrumental variables estimation has a bigger impact on property crime than on violent crime. All four of the instrumental variables estimates of legalized abortion on property crime are negative (although again less precisely estimated).

The simple fact is that when you do a better job of measuring abortion, the results get much stronger. This is exactly what you expect of a theory that is true: doing empirical work closer to the theory should yield better results than empirical work much more loosely reflecting the theory. The estimates without population controls, but including state-year interactions, are as big or bigger than what is in our original paper. As would be expected (since the unwantedness channel is not the only channel through which abortion is acting to reduce crime), the coefficients we obtain shrink when we include population controls. But, especially for violent crime, a large impact of abortion persists even when one measures arrests per capita.

The results we show in this new table are consistent with the impact of abortion on crime that we find in our three other types of analyses we presented in the original paper using different sources of variation. These results are consistent with the unwantedness hypothesis.

No doubt there will be future research that attempts to overturn our evidence on legalized abortion. Perhaps they will even succeed. But this one does not.

http://delong.typepad.com/sdj/2007/11/f ... cs-cl.html

Freakonomics Clones

I have a review of Freakonomics clones in the Chronicle of Higher Education Review http://chronicle.com/weekly/v54/i11/11b01501.htm:

In the beginning were the Steves--Steve Dubner and Steve Levitt, that is. And Steve Dubner interviewed Steve Levitt, who taught at the University of Chicago and had won the American Economic Association's Clark Medal as the outstanding young economist in his two-year cohort. And Steve Dubner and Steve Levitt begat, or conceived or brought forth, Freakonomics, which sold many copies and populated the land. And the publishers of America looked upon Freakonomics, and saw that it was good.

And the publishers of America said, "Let us commission and publish many books sort-of like Freakonomics, for here is a previously-unexploited market segment, and there is unexpectedly-high demand for books that use economists' reasoning presented in clear prose to investigate and explain curious events and patterns in our social life. And let there be marketing campaigns. And TV appearances. And review copies."

And Basic Books and Robert Frank begat The Economic Naturalist. And the Free Press and Steven Landsburg begat More Sex Is Safer Sex. And Dutton Press and Tyler Cowen begat Discover Your Inner Economist. And they were fruitful, and multiplied, and replenished the Earth, and subdued it: and had dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the Earth.

And there was evening and there was morning, another day...

My favorite is Tyler's Discover Your Inner Economist.

Maybe Money Does Make the World Go Round

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In the beginning were the Steves — Steven D. Levitt and Stephen J. Dubner, that is. And Dubner interviewed Levitt, who teaches at the University of Chicago and had won the American Economic Association's Clark Medal as the outstanding young economist in his two-year cohort. And Dubner and Levitt brought forth Freakonomics (William Morrow, 2005), which sold many copies and populated the land. And the publishers of America looked upon Freakonomics and saw that it was good.

And the publishers of America said, "Let us commission and publish many books sort of like Freakonomics, for here is a previously unexploited market segment, books that use economists' reasoning presented in clear prose to investigate and explain curious events and patterns in our lives."

And Basic Books and Robert H. Frank begat The Economic Naturalist (2007). And Free Press and Steven E. Landsburg begat More Sex Is Safer Sex (2007). And Dutton Press and Tyler Cowen begat Discover Your Inner Economist (2007).

If you have not read Freakonomics, read it first. Levitt's ideas and work are justly respected by economists, and he and Dubner have done a very good job of applying economic principles to social patterns involving crime, abortion, drug dealing, parenting, and other matters. I don't think they get every issue right, but they do make every issue they tackle accessibly interesting. And though their discussions are provocative, the provocation is appropriately secondary to the logic.

If you have read Freakonomics and are a liberal, read Cowen's Discover Your Inner Economist for elucidating discussion toward the libertarian-conservative end of the spectrum. If you have read Freakonomics and are a conservative, read Frank's The Economic Naturalist for equally admirable discussion toward the social-democratic end. Either way you'll find yourself more intellectually balanced.

Consider, for example, Cowen's discussion of tourists from affluent countries who travel in poor countries and find local guides and beggars waiting outside hotels. For the guides and beggars, waiting for the rare generous tip or gift is better than other available options — but not much better. More generous and well-intentioned visitors do not improve the well-being of local guides so much as they simply multiply their numbers. People who would otherwise be doing something useful wait instead for the relatively big score, and increased generosity becomes a social loss.

So what should an ethical liberal do? Many flint-hearted libertarians anxious to cast scorn on woolly-headed liberals would stop at this point, smugly pointing out that liberal generosity is counterproductive. Cowen goes a step further, and asks what a non-woolly-headed liberal who actually wanted to help would do. He has a simple answer: Get off the beaten track. Find somebody who is both poor — not just looking poorer than they are in the hope of attracting generosity — and busy doing something productive and useful. Give them the money. As Cowen puts it, "If you are going to give, pick the poor person who is expecting it least." That accomplishes the most efficient transfer of wealth.

Frank makes conservatives think about markets as good but flawed social instruments. Over the past couple of decades, the Cornell professor has asked his students to write 500 words on what he terms "economic naturalism": Using a principle of economics taught in the course, he instructs, "pose and answer an interesting question about some pattern of events or behavior that you personally have observed." The Economic Naturalist is made up of Frank's own best answers to that question, combined with credited and rewritten contributions from his students.

My favorite comes from Lonnie Fox: Why don't top-ranked private universities charge higher tuitions than lower-ranked ones? Fox's answer is that capable students are both customers for and producers of college educations. A college with a higher-ranked student body will have more challenging classes attractive to high-ranked students. A college is selling not just the services of its faculty and library but the chance to interact with other smart, lively, and curious students. Were Yale to raise its tuition to a level at which it began losing significant numbers of students to cheaper Wesleyan, it would find that some of its appeal to top-ranked students had vanished. "The top-ranked school," Frank argues, "needs its most accomplished students every bit as much as they need it."

My second favorite contribution to the book is by Thomas Gellert, on the demise of Caspian Sea sturgeon since the collapse of the Soviet Union starting in 1989. Before then, only two political jurisdictions bordered the Caspian Sea: Iran and the U.S.S.R. Now Iran, Russia, Kazakhstan, Turkmenistan, and Azerbaijan all border it and have been unable to negotiate fishing limits. The Caspian sturgeon population, and thus the world production of Beluga caviar, has suffered as a result.

The pop-econ genre's defect is oversimplification. Too often case studies read like just-so stories, things that might be true but that might not. The Economic Naturalist makes sense of the world, but so did Lamarck, who argued that giraffes' long necks spring from generations of giraffes each trying very hard to stretch their own individual necks to reach higher leaves, and then passing those stretched necks down to descendants. Ashees Jain may have been a good student at Cornell, but do we really want to say that the reason for the absence of top-ranked for-profit universities is that gifts to nonprofit universities are tax deductible while tuition payments to both nonprofits and for-profits are not? Surely there is more to it than that. Or take Fox's tuition explanation. We here at Berkeley charge one-third the tuition of Stanford. Our students like a place where their peers don't regard themselves as rich. We lose students who believe that the extra $80,000 is well worth paying to get Stanford's smaller class sizes and better physical plant.

Oversimplification might be a price worth paying for the pleasures of an economic window on the world. Provocation for provocation's sake, however, is not.

Which brings us to Landsburg's book, the weakest of the batch. Landsburg, of the University of Rochester, works hard too hard — at being counterintuitive and shocking. Is it true that, as far as AIDS is concerned, "more sex is safer sex"? Probably not. Not only would the chaste have to become more adventurous, but they would have to become more adventurous in a way that sufficiently reduces the sexual contact that the already adventurous have with each other. That is, the key is not more sex but the shift from very risky to only somewhat risky sex — not quite what the title advertises.

I also refuse to believe Landsburg is serious in his argument that Americans should not care about the looting of Baghdad's museums. Landsburg claims that "water in the aggregate is priceless. ... But ... we don't cry every time someone spills a bucket of water. ... Likewise, antiquities in the aggregate enrich our lives ... but ... we don't have to cry every time someone loots a museum." We cry over destruction or loss when the things that are destroyed or lost are valuable. A bucket of water isn't valuable, so we don't cry over it — unless we're in the desert, where it is valuable, and then we do. If I thought Landsburg was sincere in his proposition, I would have to reach certain judgments about him that I would rather not.

You could read his book if you have read the others and are insatiably hungry for more.

Or you could wait — another's bound to come along soon. Economics dictates it, as some economist will no doubt elucidate for us in enjoyable if unnuanced fashion.

November 06, 2007 at 08:38 AM in Books, Economics: Economists, Economics: Environment, Sorting: DeLong: CV, Sorting: DeLong: Writings, Sorting: Front Page, Sorting: Pieces of the Occasion | Permalink