Showing papers by "University of Chicago published in 2002"

ASSESSING "NEIGHBORHOOD EFFECTS": Social Processes and New Directions in Research

Abstract: ▪ Abstract This paper assesses and synthesizes the cumulative results of a new “neighborhood-effects” literature that examines social processes related to problem behaviors and health-related outcomes. Our review identified over 40 relevant studies published in peer-reviewed journals from the mid-1990s to 2001, the take-off point for an increasing level of interest in neighborhood effects. Moving beyond traditional characteristics such as concentrated poverty, we evaluate the salience of social-interactional and institutional mechanisms hypothesized to account for neighborhood-level variations in a variety of phenomena (e.g., delinquency, violence, depression, high-risk behavior), especially among adolescents. We highlight neighborhood ties, social control, mutual trust, institutional resources, disorder, and routine activity patterns. We also discuss a set of thorny methodological problems that plague the study of neighborhood effects, with special attention to selection bias. We conclude with promising ...

Genetic Structure of Human Populations

Abstract: We studied human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 populations. Within-population differences among individuals account for 93 to 95% of genetic variation; differences among major groups constitute only 3 to 5%. Nevertheless, without using prior information about the origins of individuals, we identified six main genetic clusters, five of which correspond to major geographic regions, and subclusters that often correspond to individual populations. General agreement of genetic and predefined populations suggests that self-reported ancestry can facilitate assessments of epidemiological risks but does not obviate the need to use genetic information in genetic association studies.

Generating samples under a Wright-Fisher neutral model of genetic variation.

Abstract: A Monte Carlo computer program is available to generate samples drawn from a population evolving according to a Wright-Fisher neutral model. The program assumes an infinite-sites model of mutation, and allows recombination, gene conversion, symmetric migration among subpopulations, and a variety of demographic histories. The samples produced can be used to investigate the sampling properties of any sample statistic under these neutral models.

NF-κB at the crossroads of life and death

Abstract: The choice between life and death is one of the major events in regulation of the immune system. T cells that specifically recognize viral or bacterial antigens are selected to survive and proliferate in response to infection, whereas those that are self-reactive are eliminated via apoptosis. Even the survival of alloreactive T cells requires their proper costimulation and, when infection subsides, the activated T cells are eliminated. A major regulator of such life or death decisions is the transcription factor NF-κB. However, NF-κB cannot function alone. A variety of mechanisms exist to modulate its activity and thereby affect the ultimate outcome of a cell's fate.

Testing Trade-Off and Pecking Order Predictions About Dividends and Debt

Abstract: Confirming predictions shared by the trade-off and pecking order models, more profitable firms and firms with fewer investments have higher dividend payouts. Confirming the pecking order model but contradicting the trade-off model, more profitable firms are less levered. Firms with more investments have less market leverage, which is consistent with the trade-off model and a complex pecking order model. Firms with more investments have lower long-term dividend payouts, but dividends do not vary to accommodate shortterm variation in investment. As the pecking order model predicts, short-term variation in investment and earnings is mostly absorbed by debt. The finance literature offers two competing models of financing decisions. In the trade-off model, firms identify their optimal leverage by weighing the costs and benefits of an additional dollar of debt. The benefits of debt include, for example, the tax deductibility of interest and the reduction of free cash flow problems. The costs of debt include potential bankruptcy costs and agency conflicts between stockholders and bondholders. At the leverage optimum, the benefit of the last dollar of debt just offsets the cost. The tradeoff model makes a similar prediction about dividends. Firms maximize value by selecting the dividend payout that equates the costs and benefits of the last dollar of dividends. Myers (1984) develops an alternative theory known as the pecking order model of financing decisions. The pecking order arises if the costs of issuing new securities overwhelm other costs and benefits of dividends and debt. The financing costs that produce pecking order behavior include the transaction costs associated with new issues and the costs that arise because of management’s superior information about the firm’s prospects and the value of its risky securities. Because of these costs, firms finance new investments first with retained earnings, then with safe debt, then with risky debt, and finally, under duress, with equity. As a result, variation in a firm’s leverage

Sloan digital sky survey: Early data release

Abstract: The Sloan Digital Sky Survey (SDSS) is an imaging and spectroscopic survey that will eventually cover approximately one-quarter of the celestial sphere and collect spectra of ≈106 galaxies, 100,000 quasars, 30,000 stars, and 30,000 serendipity targets. In 2001 June, the SDSS released to the general astronomical community its early data release, roughly 462 deg2 of imaging data including almost 14 million detected objects and 54,008 follow-up spectra. The imaging data were collected in drift-scan mode in five bandpasses (u, g, r, i, and z); our 95% completeness limits for stars are 22.0, 22.2, 22.2, 21.3, and 20.5, respectively. The photometric calibration is reproducible to 5%, 3%, 3%, 3%, and 5%, respectively. The spectra are flux- and wavelength-calibrated, with 4096 pixels from 3800 to 9200 A at R ≈ 1800. We present the means by which these data are distributed to the astronomical community, descriptions of the hardware used to obtain the data, the software used for processing the data, the measured quantities for each observed object, and an overview of the properties of this data set.

Differences of Opinion and the Cross Section of Stock Returns

Abstract: We provide evidence that stocks with higher dispersion in analysts’ earnings forecasts earn lower future returns than otherwise similar stocks. This effect is most pronounced in small stocks and stocks that have performed poorly over the past year. Interpreting dispersion in analysts’ forecasts as a proxy for differences in opinion about a stock, we show that this evidence is consistent with the hypothesis that prices will ref lect the optimistic view whenever investors with the lowest valuations do not trade. By contrast, our evidence is inconsistent with a view that dispersion in analysts’ forecasts proxies for risk. IN THIS PAPER WE ANALYZE THE ROLE of dispersion in analysts’ earnings forecasts in predicting the cross section of future stock returns. We find that stocks with higher dispersion in analysts’ earnings forecasts earn significantly lower future returns than otherwise similar stocks. In particular, a portfolio of stocks in the highest quintile of dispersion underperforms a portfolio of stocks in the lowest quintile of dispersion by 9.48 percent per year. This effect is strongest in small stocks, and stocks that have performed poorly over the past year. Our results are robust to various risk-adjustment techniques, and are inconsistent with an interpretation of dispersion in analysts’ forecasts as a proxy for risk. We postulate that dispersion in analysts’ earnings forecasts can be viewed as a proxy for differences of opinion among investors. Differences of opinion are typically modeled via dogmatic beliefs or asymmetric information sets, and have been included in numerous models that relax the standard

Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Main Galaxy Sample

Abstract: We describe the algorithm that selects the main sample of galaxies for spectroscopy in the Sloan Digital Sky Survey (SDSS) from the photometric data obtained by the imaging survey. Galaxy photometric properties are measured using the Petrosian magnitude system, which measures flux in apertures determined by the shape of the surface brightness profile. The metric aperture used is essentially independent of cosmological surface brightness dimming, foreground extinction, sky brightness, and the galaxy central surface brightness. The main galaxy sample consists of galaxies with r-band Petrosian magnitudes r ≤ 17.77 and r-band Petrosian half-light surface brightnesses μ50 ≤ 24.5 mag arcsec-2. These cuts select about 90 galaxy targets per square degree, with a median redshift of 0.104. We carry out a number of tests to show that (1) our star-galaxy separation criterion is effective at eliminating nearly all stellar contamination while removing almost no genuine galaxies, (2) the fraction of galaxies eliminated by our surface brightness cut is very small (~0.1%), (3) the completeness of the sample is high, exceeding 99%, and (4) the reproducibility of target selection based on repeated imaging scans is consistent with the expected random photometric errors. The main cause of incompleteness is blending with saturated stars, which becomes more significant for brighter, larger galaxies. The SDSS spectra are of high enough signal-to-noise ratio (S/N > 4 per pixel) that essentially all targeted galaxies (99.9%) yield a reliable redshift (i.e., with statistical error less than 30 km s-1). About 6% of galaxies that satisfy the selection criteria are not observed because they have a companion closer than the 55'' minimum separation of spectroscopic fibers, but these galaxies can be accounted for in statistical analyses of clustering or galaxy properties. The uniformity and completeness of the galaxy sample make it ideal for studies of large-scale structure and the characteristics of the galaxy population in the local universe.

1,25-Dihydroxyvitamin D3 is a negative endocrine regulator of the renin-angiotensin system

Abstract: Inappropriate activation of the renin-angiotensin system, which plays a central role in the regulation of blood pressure, electrolyte, and volume homeostasis, may represent a major risk factor for hypertension, heart attack, and stroke. Mounting evidence from clinical studies has demonstrated an inverse relationship between circulating vitamin D levels and the blood pressure and/or plasma renin activity, but the mechanism is not understood. We show here that renin expression and plasma angiotensin II production were increased severalfold in vitamin D receptor-null (VDR-null) mice, leading to hypertension, cardiac hypertrophy, and increased water intake. However, the salt- and volume-sensing mechanisms that control renin synthesis are still intact in the mutant mice. In wild-type mice, inhibition of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] synthesis also led to an increase in renin expression, whereas 1,25(OH)(2)D(3) injection led to renin suppression. We found that vitamin D regulation of renin expression was independent of calcium metabolism and that 1,25(OH)(2)D(3) markedly suppressed renin transcription by a VDR-mediated mechanism in cell cultures. Hence, 1,25(OH)(2)D(3) is a novel negative endocrine regulator of the renin-angiotensin system. Its apparent critical role in electrolytes, volume, and blood pressure homeostasis suggests that vitamin D analogues could help prevent or ameliorate hypertension.

Psychiatric disorders in youth in juvenile detention.

Abstract: Background Given the growth of juvenile detainee populations, epidemiologic data on their psychiatric disorders are increasingly important. Yet, there are few empirical studies. Until we have better epidemiologic data, we cannot know how best to use the system's scarce mental health resources. Methods Using the Diagnostic Interview Schedule for Children version 2.3, interviewers assessed a randomly selected, stratified sample of 1829 African American, non-Hispanic white, and Hispanic youth (1172 males, 657 females, ages 10-18 years) who were arrested and detained in Cook County, Illinois (which includes Chicago and surrounding suburbs). We present 6-month prevalence estimates by demographic subgroups (sex, race/ethnicity, and age) for the following disorders: affective disorders (major depressive episode, dysthymia, manic episode), anxiety (panic, separation anxiety, overanxious, generalized anxiety, and obsessive-compulsive disorders), psychosis, attention-deficit/hyperactivity disorder, disruptive behavior disorders (oppositional defiant disorder, conduct disorder), and substance use disorders (alcohol and other drugs). Results Nearly two thirds of males and nearly three quarters of females met diagnostic criteria for one or more psychiatric disorders. Excluding conduct disorder (common among detained youth), nearly 60% of males and more than two thirds of females met diagnostic criteria and had diagnosis-specific impairment for one or more psychiatric disorders. Half of males and almost half of females had a substance use disorder, and more than 40% of males and females met criteria for disruptive behavior disorders. Affective disorders were also prevalent, especially among females; more than 20% of females met criteria for a major depressive episode. Rates of many disorders were higher among females, non-Hispanic whites, and older adolescents. Conclusions These results suggest substantial psychiatric morbidity among juvenile detainees. Youth with psychiatric disorders pose a challenge for the juvenile justice system and, after their release, for the larger mental health system.

The u'g'r'i'z' Standard-Star System

Abstract: We present the 158 standard stars that define the u'g'r'i'z' photometric system. These stars form the basis for the photometric calibration of the Sloan Digital Sky Survey. The defining instrument system and filters, the observing process, the reduction techniques, and the software used to create the stellar network are all described. We briefly discuss the history of the star selection process, the derivation of a set of transformation equations for the UBVRCIC system, and plans for future work.

The Paradox of Self-Stigma and Mental Illness

Abstract: Published narratives by persons with serious mental illness eloquently describe the harmful effects of stigma on self-esteem and self-efficacy. However, a more careful review of the research literature suggests a paradox; namely, personal reactions to the stigma of mental illness may result in significant loss in self-esteem for some, while others are energized by prejudice and express righteous anger. Added to this complexity is a third group: persons who neither lose self-esteem nor become righteously angry at stigma, instead seemingly ignoring the effects of public prejudice altogether. This article draws on research from social psychologists on self-stigma in other minority groups to explain this apparent paradox. We describe a situational model of the personal response to mental illness stigma based on the collective representations that are primed in that situation, the person's perception of the legitimacy of stigma in the situation, and the person's identification with the larger group of individuals with mental illness. Implications for a research program on the personal response to mental illness stigma are discussed.

Does distance still matter? The information revolution in small business lending

Abstract: The distance between small firms and their lenders is increasing, and they are communicating in more impersonal ways. After documenting these systematic changes, we demonstrate they do not arise from small firms locating differently, consolidation in the banking industry, or biases in the sample. Instead, improvements in lender productivity appear to explain our findings. We also find distant firms no longer have to be the highest quality credits, indicating they have greater access to credit. The evidence indicates there has been substantial development of the financial sector, even in areas such as small business lending.

The antiphospholipid syndrome.

Abstract: The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the clinical association of antiphospholipid autoantibodies (aPL) with a syndrome of hypercoagulability that can affect any blood vessel, irrespective of type or size. Involvement of larger vessels, such as arteries or veins, manifests in the form of thrombosis or embolism, whereas involvement of smaller vessels, including capillaries, arterioles, and venules, manifests as thrombotic microangiopathy. Virtually any organ in the body, including the kidney, can be affected. Here, we review the basic principles and recent advances in our understanding of APS, and discuss the broad spectrum of renal diseases that have been observed in association with this syndrome. We also discuss the impact that APS may have on pre-existing renal disease as well as current recommendations for treatment of APS.

Prophylactic Oophorectomy in Carriers of BRCA1 or BRCA2 Mutations

Abstract: Background Data concerning the efficacy of bilateral prophylactic oophorectomy for reducing the risk of gynecologic cancer in women with BRCA1 or BRCA2 mutations are limited. We investigated whether this procedure reduces the risk of cancers of the coelomic epithelium and breast in women who carry such mutations. Methods A total of 551 women with disease-associated germ-line BRCA1 or BRCA2 mutations were identified from registries and studied for the occurrence of ovarian and breast cancer. We determined the incidence of ovarian cancer in 259 women who had undergone bilateral prophylactic oophorectomy and in 292 matched controls who had not undergone the procedure. In a subgroup of 241 women with no history of breast cancer or prophylactic mastectomy, the incidence of breast cancer was determined in 99 women who had undergone bilateral prophylactic oophorectomy and in 142 matched controls. The length of postoperative follow-up for both groups was at least eight years. Results Six women who underwent proph...

Instant neural control of a movement signal.

Abstract: Hands-free operation of a cursor can be achieved by a few neurons in the motor cortex. The activity of motor cortex (MI) neurons conveys movement intent sufficiently well to be used as a control signal to operate artificial devices1,2,3, but until now this has called for extensive training or has been confined to a limited movement repertoire2,3. Here we show how activity from a few (7–30) MI neurons can be decoded into a signal that a monkey is able to use immediately to move a computer cursor to any new position in its workspace (14° × 14° visual angle). Our results, which are based on recordings made by an electrode array that is suitable for human use4,5, indicate that neurally based control of movement may eventually be feasible in paralysed humans.

Hsp90 as a capacitor of phenotypic variation

Abstract: Heat-shock protein 90 (Hsp90) chaperones the maturation of many regulatory proteins and, in the fruitfly Drosophila melanogaster, buffers genetic variation in morphogenetic pathways. Levels and patterns of genetic variation differ greatly between obligatorily outbreeding species such as fruitflies and self-fertilizing species such as the plant Arabidopsis thaliana. Also, plant development is more plastic, being coupled to environmental cues. Here we report that, in Arabidopsis accessions and recombinant inbred lines, reducing Hsp90 function produces an array of morphological phenotypes, which are dependent on underlying genetic variation. The strength and breadth of Hsp90's effects on the buffering and release of genetic variation suggests it may have an impact on evolutionary processes. We also show that Hsp90 influences morphogenetic responses to environmental cues and buffers normal development from destabilizing effects of stochastic processes. Manipulating Hsp90's buffering capacity offers a tool for harnessing cryptic genetic variation and for elucidating the interplay between genotypes, environments and stochastic events in the determination of phenotype.

Ferreting out Tunneling: An Application to Indian Business Groups

Abstract: Owners of business groups are often accused of expropriating minority shareholders by tunneling resources from e rms where they have low cash e ow rights to e rms where they have high cash e ow rights. In this paper we propose a general methodology to measure the extent of tunneling activities. The methodology rests on isolating and then testing the distinctive implications of the tunneling hypothesis for the propagation of earnings shocks across e rms within a group. When we apply our methodology to data on Indian business groups, we e nd a signie cant amount of tunneling, much of it occurring via nonoperating components of proe t. I. INTRODUCTION Weak corporate law and lax enforcement mechanisms raise fears of expropriation for minority shareholders around the world. These fears seem especially warranted in the presence of business groups, a common organizational form in many developed and developing countries. In a business group, a single shareholder (or a family) completely controls several independently traded e rms and yet has signie cant cash e ow rights in only a few of them. 1 This discrepancy in cash e ow rights between the different e rms he controls creates strong incentives to expropriate. The controlling shareholder will want to transfer, or tunnel, proe ts across e rms, moving them from e rms where he has

Banks as Liquidity Providers: An Explanation for the Coexistence of Lending and Deposit-Taking

Abstract: What ties together the traditional commercial banking activities of deposittaking and lending? We argue that since banks often lend via commitments, their lending and deposit-taking may be two manifestations of one primitive function: the provision of liquidity on demand. There will be synergies between the two activities to the extent that both require banks to hold large balances of liquid assets: If deposit withdrawals and commitment takedowns are imperfectly correlated, the two activities can share the costs of the liquid-asset stockpile. We develop this idea with a simple model, and use a variety of data to test the model empirically. WHAT ARE THE DEF INING CHARACTERISTICS of a bank? Both the legal definition in the United States and the standard answer from economists is that commercial banks are institutions that engage in two distinct types of activities, one on each side of the balance sheet—deposit-taking and lending. More precisely, deposit-taking involves issuing claims that are riskless and demandable, that is, claims that can be redeemed for a fixed value at any time. Lending involves acquiring costly information about opaque borrowers, and extending credit based on this information. A great deal of theoretical and empirical analysis has been devoted to understanding the circumstances under which each of these two activities might require the services of an intermediary, as opposed to being implemented in arm’s-length securities markets. While much has been learned from this work, with few exceptions it has not addressed a fundamental question: why is it important that one institution carry out both functions

Optimizing rating scale category effectiveness.

Abstract: Rating scales are employed as a means of extracting more information out of an item than would be obtained from a mere "yes/no", "right/wrong" or other dichotomy. But does this additional information increase measurement accuracy and precision? Eight guidelines are suggested to aid the analyst in optimizing the manner in which rating scales categories cooperate in order to improve the utility of the resultant measures. Though these guidelines are presented within the context of Rasch analysis, they reflect aspects of rating scale functioning which impact all methods of analysis. The guidelines feature rating-scale-based data such as category frequency, ordering, rating-to-measure inferential coherence, and the quality of the scale from measurement and statistical perspectives. The manner in which the guidelines prompt recategorization or reconceptualization of the rating scale is indicated. Utilization of the guidelines is illustrated through their application to two published data sets.

The Equity Premium

Abstract: We estimate the equity premium using dividend and earnings growth rates to measure the expected rate of capital gain. Our estimates for 1951 to 2000, 2.55 percent and 4.32 percent, are much lower than the equity premium produced by the average stock return, 7.43 percent. Our evidence suggests that the high average return for 1951 to 2000 is due to a decline in discount rates that produces a large unexpected capital gain. Our main conclusion is that the average stock return of the last half-century is a lot higher than expected. THE EQUITY PREMIUM—the difference between the expected return on the market portfolio of common stocks and the risk-free interest rate—is important in portfolio allocation decisions, estimates of the cost of capital, the debate about the advantages of investing Social Security funds in stocks, and many other applications. The average return on a broad portfolio of stocks is typically used to estimate the expected market return. The average real return for 1872 to 2000 on the S&P index ~a common proxy for the market portfolio, also used here! is 8.81 percent per year. The average real return on sixmonth commercial paper ~a proxy for the risk-free interest rate! is 3.24 percent. This large spread ~5.57 percent! between the average stock return and the interest rate is the source of the so-called equity premium puzzle: Stock returns seem too high given the observed volatility of consumption ~Mehra and Prescott ~1985!!. We use fundamentals ~dividends and earnings! to estimate the expected stock return. Along with other evidence, the expected return estimates from fundamentals help us judge whether the realized average return is high or low relative to the expected value. The logic of our approach is straightforward. The average stock return is the average dividend yield plus the average rate of capital gain:

Bond Risk Premia

Abstract: This paper studies time variation in expected excess bond returns. We run regressions of annual excess returns on forward rates. We find that a single factor predicts 1-year excess returns on 1-5 year maturity bonds with an R2 up to 43%. The single factor is a tent-shaped linear function of forward rates. The return forecasting factor has a clear business cycle correlation: Expected returns are high in bad times, and low in good times, and the return-forecasting factor forecasts long-run output growth. The return-forecasting factor also forecasts stock returns, suggesting a common time-varying premium for real interest rate risk. The return forecasting factor is poorly related to level, slope, and curvature movements in bond yields. Therefore, it represents a source of yield curve movement not captured by most term structure models. Though the return-forecasting factor accounts for more than 99% of the time-variation in expected excess bond returns, we find additional, very small factors that forecast equally small differences between long term bond returns, and hence statistically reject a one-factor model for expected returns.

Protein Nanoarrays Generated By Dip-Pen Nanolithography

Abstract: Dip-pen nanolithography was used to construct arrays of proteins with 100- to 350-nanometer features. These nanoarrays exhibit almost no detectable nonspecific binding of proteins to their passivated portions even in complex mixtures of proteins, and therefore provide the opportunity to study a variety of surface-mediated biological recognition processes. For example, reactions involving the protein features and antigens in complex solutions can be screened easily by atomic force microscopy. As further proof-of-concept, these arrays were used to study cellular adhesion at the submicrometer scale.

Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample

Abstract: We describe the algorithm for selecting quasar candidates for optical spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected via their nonstellar colors in ugriz broadband photometry and by matching unresolved sources to the FIRST radio catalogs. The automated algorithm is sensitive to quasars at all redshifts lower than z ~ 5.8. Extended sources are also targeted as low-redshift quasar candidates in order to investigate the evolution of active galactic nuclei (AGNs) at the faint end of the luminosity function. Nearly 95% of previously known quasars are recovered (based on 1540 quasars in 446 deg2). The overall completeness, estimated from simulated quasars, is expected to be over 90%, whereas the overall efficiency (quasars/quasar candidates) is better than 65%. The selection algorithm targets ultraviolet excess quasars to i* = 19.1 and higher redshift (z 3) quasars to i* = 20.2, yielding approximately 18 candidates deg-2. In addition to selecting "normal" quasars, the design of the algorithm makes it sensitive to atypical AGNs such as broad absorption line quasars and heavily reddened quasars.

The Police Officer's Dilemma: Using Ethnicity to Disambiguate Potentially Threatening Individuals

Abstract: Using a simple videogame, the effect of ethnicity on shoot/don’t shoot decisions was examined. African American or White targets, holding guns or other objects, appeared in complex backgrounds. Participants were told to “shoot” armed targets and to “not shoot” unarmed targets. In Study 1, White participants made the correct decision to shoot an armed target more quickly if the target was African American than if he was White, but decided to “not shoot” an unarmed target more quickly if he was White. Study 2 used a shorter time window, forcing this effect into error rates. Study 3 replicated Study 1’s effects and showed that the magnitude of bias varied with perceptions of the cultural stereotype and with levels of contact, but not with personal racial prejudice. Study 4 revealed equivalent levels of bias among both African American and White participants in a community sample. Implications and potential underlying mechanisms are discussed.

Social Networks and Technology Adoption in Northern Mozambique

Abstract: Despite their potentially strong impact on poverty, agricultural innovations are often adopted slowly. Using a unique household dataset on sunflower adoption in Mozambique, we analyse whether and how individual adoption decisions depend upon the choices of others in the same social networks. Since farmers anticipate that they will share information with others, we expect farmers to be more likely to adopt when they know many other adopters. Dynamic considerations, however, suggest that farmers who know many adopters might strategically delay adoption and to free-ride on the information gathered by others. We present empirical evidence which shows that the relationship between the probability of adoption and the number of known adopters is shaped as an inverse-U. In line with information sharing, the network effect is stronger for farmers who report discussing agriculture with others. The data contains information which is needed to ameliorate the identification issues that commonly arise in this context. In particular social networks are precisely identified, and in addition we can control for village heterogeneity and endogenous group information.