Rir é o melhor remédio

Uma página bem legal no Facebook é a "Drama Universitário".

O site, também muito bom, é este aqui.

Coca Cola e o financiamento de pesquisas

Saiu no The New York Times (via JB, adaptado): a Coca Cola, maior produtora mundial de refrigerantes, financiou estudos que apresentam uma nova solução para combater a epidemia de obesidade mundial: para manter um peso saudável, as calorias não importam mas sim os exercícios físicos.

A Coca Cola apoia uma organização sem fins lucrativos, denominada Global Energy Balance Network, que tem promovido a ideia de que os americanos preocupados com um estilo de vida saudável estão mais fixados nas quantidades de comida e bebida que ingerem, quando deviam realmente preocupar-se com o exercício físico.

Segundo a reportagem, os demais cientistas garantem que esta mensagem é errada e faz parte da estratégia da Coca Cola para desvalorizar o papel que tem sido atribuído aos refrigerantes no aumento da obesidade e da diabetes tipo 2.

A polémica surge numa altura em que, tanto nos Estados Unidos como noutras regiões do globo, se verifica um esforço da comunidade médica e científica para incentivar a aplicação de taxas sobre os refrigerantes. Em Portugal, o diretor do Programa Nacional para a Diabetes já veio defender que as bebidas com elevado teor de açúcar devem ter uma referência aos malefícios que provocam, "tal como acontece para o tabaco e deveria existir para o sal". A posição de José Manuel Boavida vai no sentido das recomendações que a Assembleia da República aprovou recentemente, no sentido da adoção de medidas de prevenção, controlo e tratamento de diabetes. Estas medidas visam, sobretudo, limitar o consumo de bebidas e outros alimentos açucarados aos menores de idade, impondo limitações também nos anúncios dirigidos às crianças.

Ao New York Times, Michele Simon, uma advogada na área da saúde pública, disse que a estratégia da Coca Cola é uma "resposta direta" às perdas da companhia. A Coca Cola fez, por outro lado, um investimento substancial na nova associação sem fins lucrativos: só no ano passado, para formalizar a Global Energy Balance Network , a empresa deu 1,5 milhões de dólares - cerca de 1,3 milhões de euros.

Leia mais: aqui

Dados contábeis, valores do mercado e retorno esperado

Resumo:

Under fairly general assumptions, expected stock returns are a linear combination of two firm fundamentals―book-to-market ratio and return on equity. This parsimonious relation is pervasive, producing expected return proxies (ERP) that predict the cross section of out-of-sample returns in 26 of 29 international equity markets. The average slope coefficient on the ERP is a highly significant 1.05. In contrast, factor-model-based proxies fail to exhibit predictive power worldwide. Integrating the model with a dynamic information structure, we show analytically, and verify empirically, that the importance of return on equity in forecasting future stock returns depends on the quality of the accounting information. This extension also reconciles our model with alternative characteristic-based forecasters. These findings suggest that a tractable accounting-based valuation model provides a unifying framework for obtaining reliable proxies of expected returns worldwide.

Chattopadhyay, Akash, Matthew R. Lyle, and Charles C.Y. Wang. "Accounting Data, Market Values, and the Cross Section of Expected Returns Worldwide." Harvard Business School Working Paper, No. 15-092, June 2015.

Endogeneidade em pesquisas de contabilidade e finanças

This paper provides a discussion of endogeneity as it relates to finance and accounting research. We discuss the textbook solutions: two-stage least squares, instrumental variables, differenced generalized method of moments (GMM) and system GMM and provide a unifying framework showing how they are related. We consider the limitations of these techniques and then detail a state-of-the-art solution, utilizing a natural experiment as a way of mitigating endogeneity and building stronger theory.

Gippel, J., Smith, T. and Zhu, Y. (2015), Endogeneity in Accounting and Finance Research: Natural Experiments as a State-of-the-Art Solution. Abacus, 51: 143–168. doi: 10.1111/abac.12048

Nada

Fonte: Aqui

José Sheinkman recebe prêmio

 

CME Group-MSRI Prize recognizes individuals who contribute original concepts in mathematical, statistical or computational methods for the study of the markets' behavior and global economics.  Scheinkman, Edwin W. Rickert Professor of Economics at Columbia University, Theodore A. Wells '29 Professor of Economics (emeritus) at Princeton University and a Research Associate at the NBER, has done extensive research on this year's panel topic.  His focus has been on building mathematical models that shed light on a variety of economic and social phenomena.  Phenomena such as: economic fluctuations, the nature of competition, the growth of cities, informal economic activity, the spatial distribution of crime, and the dynamics of price bubbles."

Other recipients of the CME Group-MSRI Prize include:

• 2013 - Dr. Bengt Holmstrom, Professor of Economics, MIT
• 2012 - Robert Shiller, Professor of Economics, Yale University; and 2013 winner of the Nobel Prize in Economics
• 2011 - Thomas Sargent, Professor of Economics, New York University; and 2011 winner of the Nobel Prize in Economics

 Fonte: aqui

Ball e Brown (1968): uma retrospectiva

Abstract:  
 
This essay provides a retrospective view on our co-authored paper, Ball and Brown (1968). The retrospective was commissioned by Gregory Waymire, then President of the American Accounting Association. It describes how we both came to be PhD students at the University of Chicago and set about researching the relation between earnings and share prices. It outlines the background against which we conducted the research, including the largely a priori accounting research literature at the time and the electric atmosphere and radical new ideas then in full bloom at Chicago. We describe some of the principal research choices we made, and their strengths and weaknesses. We also describe the reception our research received and how the related literature subsequently unfolded.

Fonte: Ray Ball and Philip R. Brown (2014) Ball and Brown (1968): A Retrospective. The Accounting Review: January 2014, Vol. 89, No. 1, pp. 1-26.

O que a próxima geração de economistas está estudando?

 

Mais explicações aqui

Metrics: combatendo ciência de baixa qualidade

“WHY most published research findings are false” is not, as the title of an academic paper, likely to win friends in the ivory tower. But it has certainly influenced people (including journalists at The Economist). The paper it introduced was published in 2005 by John Ioannidis, an epidemiologist who was then at the University of Ioannina, in Greece, and is now at Stanford. It exposed the ways, most notably the overinterpreting of statistical significance in studies with small sample sizes, that scientific findings can end up being irreproducible—or, as a layman might put it, wrong.
Dr Ioannidis has been waging war on sloppy science ever since, helping to develop a discipline called meta-research (ie, research about research). Later this month that battle will be institutionalised, with the launch of the Meta-Research Innovation Centre at Stanford.

METRICS, as the new laboratory is to be known for short, will connect enthusiasts of the nascent field in such corners of academia as medicine, statistics and epidemiology, with the aim of solidifying the young discipline. Dr Ioannidis and the lab’s co-founder, Steven Goodman, will (for this is, after all, science) organise conferences at which acolytes can meet in the world of atoms, rather than just online. They will create a “journal watch” to monitor scientific publishers’ work and to shame laggards into better behaviour. And they will spread the message to policymakers, governments and other interested parties, in an effort to stop them making decisions on the basis of flaky studies. All this in the name of the centre’s nerdishly valiant mission statement: “Identifying and minimising persistent threats to medical-research quality.”

The METRICS system

Irreproducibility is one such threat—so much so that there is an (admittedly tongue-in-cheek) publication called the Journal of Irreproducible Results. Some fields are making progress, though. In psychology, the Many Labs Replication Project, supported by the Centre for Open Science, an institute of the University of Virginia, has re-run 13 experiments about widely accepted theories. Only ten were validated. The centre has also launched what it calls the Cancer Biology Reproducibility Project, to look at 50 recent oncology studies.
Until now, however, according to Dr Ioannidis, no one has tried to find out whether such attempts at revalidation have actually had any impact on the credibility of research. METRICS will try to do this, and will make recommendations about how future work might be improved and better co-ordinated—for the study of reproducibility should, like any branch of science, be based on evidence of what works and what does not.

Wasted effort is another scourge of science that the lab will look into. A recent series of articles in the Lancet noted that, in 2010, about $200 billion (an astonishing 85% of the world’s spending on medical research) was squandered on studies that were flawed in their design, redundant, never published or poorly reported. METRICS will support efforts to tackle this extraordinary inefficiency, and will itself update research about the extent to which randomised-controlled trials acknowledge the existence of previous investigations of the same subject. If the situation has not improved, METRICS and its collaborators will try to design new publishing practices that discourage bad behaviour among scientists.
There is also Dr Ioannidis’s pet offender: publication bias. Not all studies that are conducted get published, and the ones which do tend to be those that have significant results. That leaves a skewed impression of the evidence.

Researchers have been studying publication bias for years, using various statistical tests. Again, though, there has been little reflection on these methods and their comparative effectiveness. They may, according to Dr Ioannidis, be giving both false negatives and false positives about whether or not publication bias exists in a particular body of studies.

Dr Ioannidis plans to run tests on the methods of meta-research itself, to make sure he and his colleagues do not fall foul of the very criticisms they make of others. “I don’t want”, he says, “to take for granted any type of meta-research is ideal and efficient and nice. I don’t want to promise that we can change the world, although this is probably what everybody has to promise to get funded nowadays.”

Fonte: aqui

Falhas Metodológicas das pesquisas empíricas em contabilidade

Some Methodological Deficiencies in Empirical Research Articles in Accounting. Accounting Horizons: September 2014
Resumo:

This paper uses a sample of the regression and behavioral papers published in The Accounting Review and the Journal of Accounting Research from September 2012 through May 2013. We argue first that the current research results reported in empirical regression papers fail adequately to justify the time period adopted for the study. Second, we maintain that the statistical analyses used in these papers as well as in the behavioral papers have produced flawed results. We further maintain that their tests of statistical significance are not appropriate and, more importantly, that these studies do not—and cannot—properly address the economic significance of the work. In other words, significance tests are not tests of the economic meaningfulness of the results. We suggest ways to avoid some but not all of these problems. We also argue that replication studies, which have been essentially abandoned by accounting researchers, can contribute to our search for truth, but few will be forthcoming unless the academic reward system is modified.

Keywords:  research methodology, statistical analysis

Received: September 2013; Accepted: May 2014 ;Published Online: May 2014

Thomas R. Dyckman and Stephen A. Zeff (2014) Some Methodological Deficiencies in Empirical Research Articles in Accounting. Accounting Horizons: September 2014, Vol. 28, No. 3, pp. 695-712.

doi: http://dx.doi.org/10.2308/acch-50818

 http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2324266

Thomas R. Dyckman is a Professor Emeritus at Cornell University and an Adjunct Professor at Florida Gulf Coast University, and Stephen A. Zeff is a Professor at Rice University.

Recomendações dos Autores:

In summary we have endeavored to make the following points:

First, authors must adequately defend their selection of the sample period by convincing the reader that the period is stable itself and in relation to periods in close proximity.

Second, the accounting academy should actively seek and reward replications as an essential element in its aspirations to be a scientific community.

Third, authors should attend to the economic significance as well as the statistical significance of their investigations.

Fourth, authors should respect the limitation of conventional hypothesis tests applied to their data, which implies enhanced caution when declaring results to be statistically significant.

Fifth, authors could consider reporting the use of statistical intervals as a way to mitigate the problems of determining the most likely alternative hypothesis and thereby the appropriate Type ll error.

Sixth, authors need to be sure that, in their “Conclusions” section, they discuss the limitations of their research and how these limitations might be overcome, as well as suggest extensions for future research.
Seventh, authors should consider the use of descriptive statistics and other approaches as a means of, or support for, establishing the validity of their research objective.

Eighth, editors should consider requiring authors of accepted papers to provide a complete description of their methodology, including data collection, accuracy, and verification

Pressão dos Pares no avião

So you’re sitting on a plane, somewhere in the back. Sweat is rising off this human stew, and in horror you watch it condense, trickling down the window glass. You slam the blind shut. Eww.

Of course the feeling is irrational—you’re flying, through the sky!—but you hate everything right now. The airline, for its stinginess. The flight attendant, for pouring you half a can of Coke, then taking the can back. But most of all, you hate your fellow passengers. You hate humanity.
Someone next to you swipes his credit card to buy an in-flight movie, which again reminds you of the insult, the nickel and diming, of air travel.

And yet. After analyzing a confidential database of passenger and time-stamped purchase records, a Stanford professor discovered that if someone next to you buys something on the plane, you’re 30 percent more likely to buy something yourself.
That’s the power of peer pressure.

In a recent working paper, Pedro Gardete looked at 65,525 transactions across 1,966 flights and more than 257,000 passengers. He parsed the data into thousands of mini-experiments such as this:

If someone beside you ordered a snack or a film, Gardete was able to see whether later you did, too. In this natural experiment, the person sitting directly in front of you was the control subject. Purchases were made on a touchscreen; that person wouldn’t have been able to see anything. If you bought something, and the person in front of you didn’t, peer pressure may have been the reason.

Because he had reservation data, Gardete could exclude people flying together, and he controlled for all kinds of other factors such as seat choice. This is purely the effect of a stranger’s choice — not just that, but a stranger whom you might be resenting because he is sitting next to you, and this is a plane.

By adding up thousands of these little experiments, Gardete, an assistant professor of marketing at Stanford, came up with an estimate. On average, people bought stuff 15 to 16 percent of the time. But if you saw someone next to you order something, your chances of buying something, too, jumped by 30 percent, or about four percentage points.

“That magnitude I really didn’t expect,” Gardete says. “It’s crazy, crazy.”

The beauty of this paper is that it looks at social influences in a controlled situation. (What’s more of a trap than an airplane seat?) These natural experiments are hard to come by.
Economists and social scientists have long wondered about the power of peer pressure, but it’s one of the trickiest research problems.

“Social effects in consumption are very hard to measure,” Gardete says. “Just think of a supermarket. The number of things happening in a supermarket are so huge that it’s very hard to measure anything.”

[...]
Fonte: aqui

Suborno no mundo

Corruption knows no boundaries, or borders, according to a new study released by The Organization for Economic Cooperation and Development.
The OECD analyzed 427 foreign bribery cases that were closed between 1999 and 2014. What the researchers found is a steady stream of illicit money exchanges between multinational businesses and public officials in both poor and rich countries.

"We have learned that bribes are being paid across sectors to officials from countries at all stages of economic development," the researchers wrote. "Corporate leadership is involved, or at least aware, of the practice of foreign bribery in most cases, rebutting perceptions of bribery as the act of rogue employees."
Although the number of foreign bribery cases resulting in a punishment has fallen since its peak in 2011, it remains historically high.


And there have been cases  affects at least 86 countries around the globe.

That should raise an eyebrow. After all, these are business executives and government officials who have actually been caught, meaning that they likely only represent a fraction of the total number involved in under the table cash exchanges. While the report doesn't name any of the corporations, finding one currently embattled by corruption accusations isn't hard. Wal-Mart, the world's largest retailers, is currently being probed for bribery in a number of countries, after the company disclosed potential violations in Mexico.

But what is truly unique about the study is the level of detail it uncovers about how the bribes are being paid, where they are being paid, why they are being paid, who is offering them, and to whom they are being offered.

 And there have been cases  affects at least 86 countries around the globe.

That should raise an eyebrow. After all, these are business executives and government officials who have actually been caught, meaning that they likely only represent a fraction of the total number involved in under the table cash exchanges. While the report doesn't name any of the corporations, finding one currently embattled by corruption accusations isn't hard. Wal-Mart, the world's largest retailers, is currently being probed for bribery in a number of countries, after the company disclosed potential violations in Mexico.
But what is truly unique about the study is the level of detail it uncovers about how the bribes are being paid, where they are being paid, why they are being paid, who is offering them, and to whom they are being offered.

 Continua aqui

Escrevendo um artigo científico

Timothy Weninger mostra (via aqui), no vídeo acima, a construção de um trabalho científico. O texto passou por 463 versões, até o final do vídeo.

Produtividade dos PHDs em Economia

“IF THE objective of graduate training in top-ranked [economics] departments is to produce successful research economists, then these graduate programmes are largely failing.” That’s the startling message from a recent paper published in the Journal of Economic Perspectives.

How did the authors of this paper reach such a pessimistic conclusion? They look at a 14,300 people who received an economics PhD from 154 American and Canadian institutions. They then find a massive database of academic papers published over a two-decade period. From that, they are able to tell how many papers each PhD graduate has produced in the six years after leaving graduate school. (Six years, by the way, is about the average time it takes for a newly-minted PhD to get tenure).

Of course, quantity is not the only measure of success. One great paper is worth more than three bad ones. So the authors create an index that adjusts the number of publications by the quality of the journal it appears in. The authors end up with what they call the "American Economic Review­-equivalent". To get published in the AER is a dream for any economist and so other journals are indexed in relation to it. An article in the Journal of Political Economy, for instance, is worth 0.67 papers in AER. A paper in Economic Theory is worth a quarter.

Some of the results are not terribly surprising. Graduates from the big-hitting universities can be extremely productive. The graduate in the 99th percentile from Harvard or MIT—that is, right at the very top of the graduating class—produces over 4 AER-equivalent papers over six years.

But the vast majority of PhD students, even at top universities, produce nowhere near that much (see chart). The number of AER-equivalent papers of the median PhD student, six years after graduation, is below 0.2 for all universities. Yes, all—even Harvard, MIT and Chicago. The 50th percentile at almost all universities has a score of 0.1. That’s equivalent to publishing one paper in a second-tier field journal over six years. 

AER-equivalent score, by percentile of graduates, after six years

What are the implications of these results? Even if you have been accepted into a top economics department, there is no guarantee that you will be a successful researcher. In fact top researchers come from a range of institutions, not just the best ones. The researcher in the 99th percentile of the typical “non-top-30” institution—that is, the 124 other universities in the authors’ sample—is better than her equivalent from a range of big-hitting institutions like Penn State and the University of Texas at Austin.

The paper probably says something about how economics PhD programmes are taught. Professors may give a disproportionate amount of time to the students that they think are most naturally gifted, while leaving the majority behind. As a result that lucky student is much more likely to have a successful publication record.

Now: the crucial question is whether economics PhD students want to be successful researchers. The authors see this as self-evident:


Our experience suggests that most students, especially at the better programs, enter graduate school planning to seek academic jobs, or at any rate, jobs that require research.

I'm not so sure: many econ PhDs that I know have no intention of becoming an academic but instead want to work for government or an NGO. And lots of people working in the upper echelons of business and government may produce research, but may not publish it in a peer-reviewed journal. Take economists at the IMF, for example, who produce working papers that may never become "proper" academic articles. The same goes for government employees who produce policy analysis.

For the vast majority of economics PhDs there is little point in being more productive. As we have shown before, there are far more PhDs produced each year than there are job openings. America produced more than 100,000 doctoral degrees between 2005 and 2009; in the same period there were just 16,000 new professorships. What's the point in killing yourself to be a productive researcher when finding an academic job is so hard?

Fonte: aqui

Grande parte dos achados publicados em Finanças são falsos positivos

Entrevista com Campbell Harvey, PHD em Chicago. Professor da Duke University. Ex-editor do Journal of Finance. Vice-preseidente da American Finance Association

Q: Investors often rely on financial research when developing strategies. Your recent findings suggest they should be wary. What did you find?

Campbell Harvey: My paper is about how we conduct research as both academics and practitioners. I was inspired by a paper published in the biomedical field that argued that most scientific tests that are published in medicine are false. I then gathered information on 315 tests that were conducted in finance. After I corrected the test statistics, I found that about half the tests were false. That is, someone was claiming a discovery when there was no real discovery.

Q: What do you mean “correcting the tests”?

Campbell Harvey: The intuition is really simple. Suppose you are trying to predict something like the returns on a portfolio of stocks. Suppose you try 200 different variables. Just by pure chance, about 10 of these variables will be declared “significant” – yet they aren’t. In my paper, I show this by randomly generating 200 variables. The simulated data is just noise, yet a number of the variables predict the portfolio of stock returns. Again, this is what you expect by chance. The contribution of my paper is to show how to correct the tests. The picture above looks like an attractive and profitable investment. The picture below shows 200 random strategies (i.e. the data are made up). The profitable investment is just the best random strategy (denoted in dark red). Hence, it is not an attractive investment — its profitability is purely by chance!

Q: So you provide a new set of research guidelines?

Campbell Harvey: Exactly. Indeed, we go back in time and detail the false research findings. We then extrapolate our model out to 2032 to give researchers guidelines for the next 18 years.

Q: What are the practical implications of your research?

Campbell Harvey: The implications are provocative. Our data mainly focuses on academic research. However, our paper applies to any financial product that is sold to investors. A financial product is, for example, an investment fund that purports to beat some benchmark such as the S&P 500. Often a new product is proposed and there are claims that it outperformed when it is run on historical data (this is commonly called “backtesting” in the industry). The claim of outperformance is challenged in our paper. You can imagine researchers on Wall Street trying hundreds if not thousands of variables. When you try so many variables, you are bound to find something that looks good. But is it really good – or just luck?

Q: What do you hope people take away from your research?

Campbell Harvey: Investors need to realize that about half of the products they are sold are false – that is, there is expected to be no outperformance in the future; they were just lucky in their analysis of historical data.

Q: What reactions have Wall Street businesses had so far to your findings?

Campbell Harvey: A number of these firms have struggled with this problem. They knew it existed (some of their products “work” just by chance). It is in their own best interest to deliver on promises to their clients. Hence, my work has been embraced by the financial community rather than spurned.

Professor Harvey’s research papers, “Evaluating Trading Strategies“, “…and the Cross-Section of Expected Returns” and “Backtesting” are available at SSRN for free download.

Fonte: aqui

Outra explicação aqui

Colaboração em Pesquisa

Quando um pesquisador vai fazer uma pesquisa, como ele escolhe o seu colaborador? Esta decisão não está baseada somente na competência do cientista, mas em variáveis que aproximam das escolhas que fazemos na nossa vida diária. Geralmente fazemos amizades com pessoas que possuem algum tipo de afinidade conosco. Esta afinidade inclui idade, gênero, time de futebol, origem e muitas outras variáveis. Uma dessas variáveis é a etnia.

Para demonstrar que isto ocorre na ciência, Wei Huang, da Universidade de Harvard, estudou mais de 2,5 milhões de artigos científicos escritos entre 1985 a 2008. Destes artigos, Huang utilizou somente aqueles que tinham mais de um autor. Usando um software que conseguia separar os nomes conforme sua procedência, Huang verificou se a etnia exercia alguma influencia nas “escolhas” acadêmicas. O leitor irá perceber que Huang é um nome de origem oriental, mais especificamente chinesa. O software indicava que Silva era de etnia portuguesa, Escobar espanhola e assim por diante.

Huang encontrou que os pesquisadores chineses tendem a fazer pesquisa com outros pesquisadores chineses. Ou seja, a etnia tem um papel muito forte na escolha do colaborador numa pesquisa acadêmica. Assim, um autor tende a escolher um pesquisador que possua características que lhe são próximas, o que denominamos de hemofilia.

O resultado da pesquisa de Huang é mais interessante quando ele analisa o impacto do periódico onde a pesquisa é publicada. Artigos escritos entre pesquisadores da mesma origem  tendem a ser publicados em periódicos de menor fator de impacto. Outra descoberta importante de Huang é que os pesquisadores que previamente eram pouco produtivos tendiam a escrever artigos com pessoas da mesma etnia.

Leia Mais: HUANG, Wei. Collaborating with People Like Me. Iza Discussion Paper 8432, agu 2014.

Flávio Cunha ganha a medalha Frisch

O economista brasileiro Flavio Cunha é um dos ganhadores da Medalha Frisch de 2014, distinção concedida a cada dois anos pela Sociedade Econométrica. Professor da Universidade da Pensilvânia, ele foi escolhido com o Nobel James Heckman, da Universidade de Chicago, e Susanne Schennach, da Universidade Brown, pelo artigo “Estimando a tecnologia da formação de habilidades cognitivas e não cognitivas”. Ele é o primeiro brasileiro a vencer o prêmio, conferido desde 1978.

Cunha escreveu vários estudos com Heckman, Nobel em 2000, mostrando a importância da educação infantil. Segundo ele, o objetivo do trabalho que ganhou a Medalha Frisch é “encontrar as equações matemáticas que descrevem o desenvolvimento de habilidades cognitivas, como matemática e língua portuguesa, e não-cognitivas, como persistência, motivação e auto-controle, do nascimento até aos 15 anos de idade.”

Ao falar das conclusões do artigo, Cunha diz que “as habilidades cognitivas respondem mais fortemente aos investimentos que ocorrem cedo na vida de uma criança”. Depois, fica cada vez mais caro tentar mudar uma criança em que se investiu pouco na primeira infância. “Em contraste, as habilidades não-cognitivas tem uma resposta mais uniforme ao longo da infância e da adolescência. É possível, desse modo, remediar baixos investimentos em habilidade cognitiva na primeira infância com investimentos mais elevados em habilidades não-cognitivas em idades mais avançadas.”

Segundo Cunha, o modelo econômico de formação de capital humano que Heckman e ele publicaram em 2007 havia sido inspirado em estudos experimentais de pequena escala, envolvendo cerca de 120 crianças. “O estudo que foi premiado confirma que as equações do modelo de 2007 são uma boa descrição do desenvolvimento de capital humano de 2 mil crianças que foram observadas desde o nascimento até os 15 anos de idade”, afirma ele.

Chegar às equações exigiu a superação de alguns problemas, diz Cunha. “Primeiro, não existia uma escala de medida para habilidades cognitivas e não-cognitivas. Por exemplo, para medir temperatura, temos a escala Celsius. Surpreendentemente, não tínhamos uma escala para medir habilidades. O artigo estabelece escalas naturais para as habilidades cognitivas e não-cognitivas”, afirma ele, explicando que, nesse caso, uma escala natural é, por exemplo, “o salário de uma pessoa na fase adulta da sua vida”. Pessoas com mais habilidades tendem a ter salários mais elevados.

Outro problema a ser superado é que as habilidades e os investimentos são medidos com muito erro. “É muito difícil quantificar o ambiente onde uma criança vive e é ainda mais difícil medir o QI de uma criança que tem 1 ou 2 anos de idade”, diz Cunha. “A técnica econométrica é matematicamente muito complicada por causa desse problema de erro de medida. Mas, se não tivéssemos resolvido esse problema, não poderíamos responder essa pergunta."

O terceiro problema, segundo ele, é que não se podiam fazer hipóteses sobre a fórmula matemática das equações. “Então, tinhamos que desenvolver uma técnica não-paramétrica, o que torna a análise um pouco mais complicada”, diz Cunha, acrescentando que uma técnica não-paramétrica é um “método estatístico que permite que a relação entre duas ou mais variáveis seja obtida sem impor qualquer orientação da teoria”.

Havia ainda um quarto problema. “Os dados eram observacionais e não experimentais. Ou seja, não tínhamos como manipular o ambiente onde as crianças cresciam para poder ver o impacto no desenvolvimento muitos anos mais tarde. Para lidar com esse tipo de problema, os economistas usam, por exemplo, variáveis que afetam diretamente o ambiente, mas apenas indiretamente o desenvolvimento de uma criança”, afirma Cunha. “Nós tivemos que estudar como adaptar essa técnica de estimação para um modelo não-paramétrico e com dados que têm muito erro de medida.”

A Sociedade Econométrica é uma instituição internacional que tem o objetivo de promover o avanço da teoria econômica em sua relação com a estatística e a matemática. “O prêmio é um incentivo a continuar nessa linha de pesquisa, pois ainda existem muitas questões em aberto”, afirma Cunha, que fez o mestrado na Escola de Pós-Graduação em Economia (EPGE) da Fundação Getulio Vargas (FGV) e é PhD pela Universidade de Chicago.

Leia mais em:

http://www.valor.com.br/brasil/3544888/brasileiro-e-um-dos-vencedores-de-premio-da-sociedade-econometrica#ixzz3Bz62jDGF

Brasileiro ganha Nobel da Matemática

RIO - Um carioca de 35 anos se tornou o primeiro brasileiro a receber a prestigiada Medalha Fields, considerada o prêmio Nobel da matemática. Artur Avila foi anunciado como merecedor da láurea máxima da União Internacional de Matemática (IMU, na sigla em inglês), durante o Congresso Internacional de Matemáticos, nesta terça-feira, quarta de manhã em Seul, na Coreia do Sul, onde o evento acontece. A medalha é entregue a cada quatro anos, a no mínimo dois e no máximo quatro profissionais com menos de 40 anos cujos trabalhos um comitê secreto julga terem sido fundamentais para o avanço da matemática. Junto com Avila, este ano a Fields foi entregue também ao canadense Manjul Bhargava, ao austríaco Martin Hairer e à iraniana Maryam Mirzakhani.

Artur Avila fez notáveis contribuições no campo dos sistemas dinâmicos, análise e outras áreas, em muitos casos provando resultados decisivos que resolveram problemas há muito tempo em aberto. Quase todo seu trabalho foi feito por meio de colaborações com cerca de 30 matemáticos de todo mundo. Para estas colaborações, Avila traz um formidável poder técnico, a engenhosidade e tenacidade de um mestre em resolver problemas e um profundo senso para questões profundas e significativas. Os feitos de Avila são muitos e abrangem uma ampla gama de tópicos. Com sua combinação de tremendo poder analítico e profunda intuição sobre sistemas dinâmicos, Artur Avila certamente continuará um líder na matemática ainda por muitos anos”, escreveu o comitê da IMU na sua justificativa para o prêmio.

Ex-aluno de duas escolas tradicionais do Rio, os colégios Santo Agostinho e São Bento, o calculista coleciona medalhas desde os 13 anos, quando ganhou um bronze na Olimpíada Brasileira de Matemática (OBM) de 1992. De lá até receber a sonhada Fields, Avila conquistou alguns ouros em outras edições da olimpíada e concluiu seu doutorado no Instituto de Matemática Pura e Aplicada (Impa), em 2011, aos 21 anos. Hoje, divide seu tempo entre o Impa, onde atua como pesquisador extraordinário, e o trabalho de diretor de pesquisa do Centro Nacional de Pesquisas Científicas da França, em Paris. À diferença do Nobel, cujos vencedores só sabem da premiação após o anúncio oficial na Suécia, os ganhadores da Medalha Fields são informados previamente. O carioca, que já havia sido cogitado para o prêmio em 2010, recebeu a notícia há dois meses, com um certo alívio.

— Há vários anos existia uma expectativa nessa direção, e realmente eu sentia isso como uma pressão sobre mim, também pela sua importância para o Brasil, que de maneira um pouco estranha nunca teve prêmios internacionais desse porte, como um Nobel. Assim, ficava um pouco pesado. A notícia da medalha teve, para mim, um primeiro efeito de alívio — conta Avila.

No Impa, a notícia sobre o prêmio foi recebida com muita festa:

— Essa medalha para o Artur vem primeiro coroar o trabalho individual dele, mas, ao mesmo tempo, é coerente com a situação da matemática brasileira — pondera César Camacho, diretor-geral do Impa. — Não é como um salto quântico. Um feito excepcional, sim, mas não fora da curva. É resultado de um longo trabalho de construção do Impa como centro de excelência da matemática mundial nos últimos 62 anos. Somos uma instituição aberta, com muitos contatos e interação com outras no exterior, e na qual tudo é feito com base no mérito.

Avila e os outros três ganhadores deste ano se juntam às outras 52 pessoas laureadas desde a primeira Medalha Fields, em 1936. O prêmio foi criado pelo canadense John Charles Fields, para “reparar” o erro do sueco Alfred Nobels, que, ao elaborar o Prêmio Nobel, em 1895, desconsiderou a matemática como ciência importante. Hoje, os ganhadores da Medalha Fields recebem 15 mil dólares canadenses (R$ 31 mil). Valor bem menor do que as 8 milhões de coroas suecas (cerca de R$ 2,7 milhões) pagos aos premiados com o Nobel. Nas 17 edições anteriores da Fields, os americanos foram os mais premiados (12 vezes). A medalha de Ávila é a primeira de um matemático da América Latina.

Continua aqui

Como os testes auxiliam a aprendizagem

TESTS have a bad reputation in education circles these days: They take time, the critics say, put students under pressure and, in the case of standardized testing, crowd out other educational priorities. But the truth is that, used properly, testing as part of an educational routine provides an important tool not just to measure learning, but to promote it.

In one study I published with Jeffrey D. Karpicke, a psychologist at Purdue, we assessed how well students remembered material they had read. After an initial reading, students were tested on some passages by being given a blank sheet of paper and asked to recall as much as possible. They recalled about 70 percent of the ideas.

Other passages were not tested but were reread, and thus 100 percent of the ideas were re-exposed. In final tests given either two days or a week later, the passages that had been tested just after reading were remembered much better than those that had been reread.

What’s at work here? When students are tested, they are required to retrieve knowledge from memory. Much educational activity, such as lectures and textbook readings, is aimed at helping students acquire and store knowledge. Various kinds of testing, though, when used appropriately, encourage students to practice the valuable skill of retrieving and using knowledge. The fact of improved retention after a quiz — called the testing effect or the retrieval practice effect — makes the learning stronger and embeds it more securely in memory.

This is vital, because many studies reveal that much of what we learn is quickly forgotten. Thus a central challenge to learning is finding a way to stem forgetting.

The question is how to structure and use tests effectively. One insight that we and other researchers have uncovered is that tests serve students best when they’re integrated into the regular business of learning and the stakes are not make-or-break, as in standardized testing. That means, among other things, testing new learning within the context of regular classes and study routines.

Students in classes with a regimen of regular low- or no-stakes quizzing carry their learning forward through the term, like compounded interest, and they come to embrace the regimen, even if they are skeptical at first. A little studying suffices at exam time — no cramming required.

Moreover, retrieving knowledge from memory is more beneficial when practice sessions are spaced out so that some forgetting occurs before you try to retrieve again. The added effort required to recall the information makes learning stronger. It also helps when retrieval practice is mixed up — whether you’re practicing hitting different kinds of baseball pitches or solving different solid geometry problems in a random sequence, you are better able later to discriminate what kind of pitch or geometry problem you’re facing and find the correct solution.

Surprisingly, researchers have also found that the most common study strategies — like underlining, highlighting and rereading — create illusions of mastery but are largely wasted effort, because they do not involve practice in accessing or applying what the students know.

When my colleagues and I took our research out of the lab and into a Columbia, Ill., middle school class, we found that students earned an average grade of A- on material that had been presented in class once and subsequently quizzed three times, compared with a C+ on material that had been presented in the same way and reviewed three times but not quizzed. The benefit of quizzing remained in a follow-up test eight months later.

Notably, Mary Pat Wenderoth, a biology professor at the University of Washington, has found that this benefit holds for women and underrepresented minorities, two groups that sometimes experience a high washout rate in fields like the sciences.

This isn’t just a matter of teaching students to be better test takers. As learners encounter increasingly complex ideas, a regimen of retrieval practice helps them to form more sophisticated mental structures that can be applied later in different circumstances. Think of the jet pilot in the flight simulator, training to handle midair emergencies. Just as it is with the multiplication tables, so it is with complex concepts and skills: effortful, varied practice builds mastery.

We need to change the way we think about testing. It shouldn’t be a white-knuckle finale to a semester’s work, but the means by which students progress from the start of a semester to its finish, locking in learning along the way and redirecting their effort to areas of weakness where more work is needed to achieve proficiency.

Standardized testing is in some respects a quest for more rigor in public education. We can achieve rigor in a different way. We can instruct teachers on the use of low-stakes quizzing in class. We can teach students the benefits of retrieval practice and how to use it in their studying outside class. These steps cost little and cultivate habits of successful learning that will serve students throughout their lives.


Henry L. Roediger III is a professor of psychology at Washington University in St. Louis and a co-author of “Make It Stick: The Science of Successful Learning.”

A version of this op-ed appears in print on July 20, 2014, on page SR12 of the New York edition with the headline: How Tests Make Us Smarter. 

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