Scaling approach to glassy stationary states of spin-glasses under chaos effects

Dynamics of spin-glasses subjected to slow continuous changes of working enviroment such as slow changes of temperature or interaction bonds are studied based on scaling arguments and numerical simulations of continuous bond changes. Such perturbations lead to a glassy stationary state where the age or domain size of the system are pinned to macroscopic but finite values due to competition between relaxation and chaos effects (rejuvenation). Flutuation-dissipation relation is also pinned to that of a finite age. The scenario explains the anomalously weak cooling rate dependece of spin glasses.Comment: Contribution to SPDSA 2004, Hayama, Japa

First direct observation of a torsional Alfvén oscillation at coronal heights

Context. Torsional Alfvén waves are promising candidates for the transport of energy across different layers of the solar atmosphere. They have been predicted theoretically for decades. Previous detections of Alfvén waves so far have however mostly relied on indirect signatures. Aims. We present the first direct observational evidence of a fully resolved torsional Alfvén oscillation of a large-scale structure occurring at coronal heights. Methods. We analysed IRIS imaging and spectral observation of a surge resulting from magnetic reconnection between active region prominence threads and surrounding magnetic field lines. Results. The IRIS spectral data provide clear evidence of an oscillation in the line-of-sight velocity with a 180° phase difference between the oscillation signatures at opposite edges of the surge flux tube. This together with an alternating tilt in the Si IV and Mg II k spectra across the flux tube and the trajectories traced by the individual threads of the surge material provide clear evidence of torsional oscillation of the flux tube. Conclusions. Our observation shows that magnetic reconnection leads to the generation of large-scale torsional Alfvén waves

The longer-term effects of human capital enrichment programs on poverty and inequality : Oportunidades in Mexico

Previous empirical research has shown that Mexico’s Oportunidades program has succeeded in increasing schooling and improving health of disadvantaged children. This paper studies the program’s potential longer-term consequences for the poverty and inequality of these children. It adapts methods developed in DiNardo, Fortin and Lemieux (1996) and incorporates existing experimental estimates of the program’s effects on human capital to analyze how Oportunidades will affect future earnings of program participants. We nonparametrically simulate earnings distributions, with and without the program, and predict that Oportunidades will increase future mean earnings but have only modest effects on poverty rates and earnings inequality.Oportunidades, Human capital, Schooling, Health, Poverty, Inequality.

The Production of Cognitive Achievement in Children: Home, School and Racial Test Score Gaps

This paper studies the determinants of children’s scores on tests of cognitive achievement in math and reading. Using rich longitudinal data on test scores, home environments, and schools, we implement alternative specifications for the production function for achievement and test their assumptions. We do not find support for commonly used restrictive models that assume test scores depend only on contemporaneous inputs or that assume conditioning in a lagged score captures the effects of all past inputs. Instead, the results show that both contemporaneous and lagged inputs matter in the production of current achievement and that it is important to allow for unobserved child-specific endowment effects and endogeneity of inputs. Using a specification that incorporates these features, we analyze sources of test score gaps between black, white and Hispanic children. The estimated model captures key patterns in the data, such as the widening of minority-white test score gaps with age, which is most pronounced for black children.Education production function, racial test score gaps, school quality, child development and cognitive achievement

A Note on Adapting Propensity Score Matching and Selection Models to Choice Based Samples

The probability of selection into treatment plays an important role in matching and selection models. However, this probability can often not be consistently estimated, because of choice-based sampling designs with unknown sampling weights. This note establishes that the selection and matching procedures can be implemented using propensity scores fit on choice-based samples with misspecified weights, because the odds ratio of the propensity score fit on the choice-based sample is monotonically related to the odds ratio of the true propensity scores.choice-based sampling, matching models, propensity scores, selection models

Ex Ante Evaluation of Social Programs

This paper discusses methods for evaluating the impacts of social programs prior to their implementation. Ex ante evaluation is useful for designing programs that achieve some optimality criteria, such as maximizing impact for a given cost. This paper illustrates through several examples the use of behavioral models in predicting the impacts of hypothetical programs. Among the programs considered are wage subsidy programs, conditional cash transfer programs, and income support programs. In some cases, the behavioral model justifies a completely nonparametric estimation strategy, even when there is no direct variation in the policy instrument. In other cases, stronger modeling and/or functional form assumptions are required to evaluate a program ex ante. We illustrate the application of ex ante evaluation methods using data from the PROGRESA school subsidy experiment in Mexico. We assess the effectiveness of the method by comparing ex ante predictions of program impacts to the impacts measured under the randomized experiment.ex-ante evaluation, matching, evaluation methods, school subsidy programs

How Beliefs about HIV Status Affect Risky Behaviors: Evidence from Malawi, Second Version

This paper examines whether and to what extent changes in beliefs about own HIV status induce changes in risky sexual behavior using data from married males living in three regions of Malawi. Risky behavior is measured as the propensity to engage in extramarital affairs. The empirical analysis is based on panel surveys for years 2006 and 2008 from the Malawi Diffusion and Ideational Change Project (MDICP), which contain detailed information on beliefs about HIV status and on sexual behaviors. Many individuals change their beliefs over time, because of opportunities to get tested for HIV and informational campaigns. We estimate the effect of belief revisions on the propensity to engage in extra-marital affairs using a panel data estimator developed by Arellano and Carrasco (2003), which accommodates unobserved heterogeneity as well as belief endogeneity arising from the dependence of current beliefs on lagged behaviors. We find that downward revisions in the belief of being HIV positive lead to an increased propensity to engage in extra-marital affairs and upward revisions to a decreased propensity. The estimates are shown to be robust to underreporting of affairs. Using our estimates and a standard epidemeological model of disease transmission, we find that increasing the responsiveness of beliefs to test results would reduce the HIV transmission rate as infected individuals reduce sexual behavior and decrease the likelihood that uninfected persons have contact with an HIV-positive person.AIDS, Malawi, Beliefs

How Beliefs About HIV Status affect Risky Behaviors: Evidence From Malawi, Second Version

This paper examines how beliefs about own HIV status affect sexual behavior. Risky behavior is measured as the propensity to engage in extramarital affairs or not use condoms. The empirical analysis is based on 2004 and 2006 data from the Malawi Diffusion and Ideational Change Project. Controlling for endogeneity between beliefs and risk-taking, we find that downward revisions in the belief of being HIV positive lead to a lower propensity to engage in extramarital affairs but have no effect on condom use. We show that the estimates provide a lower bound when there is measurement error in reported extra-marital affairs.Beliefs,AIDS,Malawi

How Beliefs about HIV Status Affect Risky Behaviors: Evidence from Malawi, Fifth Version

This paper examines how beliefs about own HIV status affect decisions to engage in risky sexual behavior using data on married males living in Malawi. Risky behavior is measured as the propensity to engage in extramarital affairs. The empirical analysis is based on panel surveys for years 2006 and 2008 from the Malawi Diffusion and Ideational Change Project (MDICP). Beliefs vary significantly over time in the data, in part because of HIV testing and informational campaigns. We estimate the effect of beliefs about own HIV status on risky behavior using a panel data estimator developed by Arellano and Carrasco (2003), which accommodates unobserved heterogeneity as well as belief endogeneity arising from the dependence of current beliefs on lagged behaviors. We find that beliefs are an important determinant of risky behavior, with downward revisions in the belief of being HIV positive increasing risky behavior and upward revisions decreasing it. We modify Arellano and Carrasco’s (2003) estimator to allow for underreporting of affairs and find the estimates to be relatively robust to underreporting. Using our estimates and a prototypical epidemiological model of disease transmission, we show that making individuals better informed about their HIV status, either by increasing the credibility of test results and/or increasing access to testing, would on net reduce the HIV transmission rate.Beliefs, Malawi, HIV

Earnings Functions and Rates of Return

The internal rate of return to schooling is a fundamental economic parameter that is often used to assess whether expenditure on education should be increased or decreased. This paper considers alternative approaches to estimating marginal internal rates of return for different schooling levels. We implement a general nonparametric approach to estimate marginal internal rates of return that take into account tuition costs, income taxes and nonlinearities in the earnings-schooling-experience relationship. The returns obtained by the more general method differ substantially from Mincer returns in levels and in their evolution over time. They indicate relatively larger returns to graduating from high school than from graduating from college, although both have been increasing over time.schooling, marginal internal rate of return, nonparametric estimation