Evaluating the impact of Mexico's quality schools program : the pitfalls of using nonexperimental data

The authors evaluate whether increasing school resources and decentralizing management decisions at the school level improves learning in a developing country. Mexico's Quality Schools Program (PEC), following many other countries and U.S. states, offers US$15,000 grants for public schools to implement five-year improvement plans that the school's staff and community design. Using a three-year panel of 74,700 schools, the authors estimate the impact of the PEC on dropout, repetition, and failure using two common nonexperimental methods-regression analysis and propensity score matching. The methods provide similar but nonidentical results. The preferred estimator, difference-in-differences with matching, reveals that participation in the PEC decreases dropout by 0.24 percentage points, failure by 0.24 percentage points, and repetition by 0.31 percentage points-an economically small but statistically significant impact. The PEC lacks measurable impact on outcomes in indigenous schools. The results suggest that a combination of increased resources and local management can produce small improvements in school outcomes, though perhaps not in the most troubled school systems.Tertiary Education,Education For All,Primary Education,Teaching and Learning,Secondary Education,Economics of Education

Globalization and the Role of Public Transfers in Redistributing Income in Latin America and the Caribbean

This paper focuses on measuring the extent to which publicly subsidized transfers in Latin America and the Caribbean redistribute income. The redi$social protection, insurance, redistribution, targeting, poverty, inequality, welfare

Prospects for Annihilating Dark Matter in the inner Galactic halo by the Cherenkov Telescope Array

We compute the sensitivity to dark matter annihilations for the forthcoming large Cherenkov Telescope Array (CTA) in several primary channels and over a range of dark matter masses from 30 GeV up to 80 TeV. For all channels, we include inverse Compton scattering of e$^\pm$ by dark matter annihilations on the ambient photon background, which yields substantial contributions to the overall gamma-ray flux. We improve the analysis over previous work by: i) implementing a spectral and morphological analysis of the gamma-ray emission; ii) taking into account the most up-to-date cosmic ray background obtained from a full CTA Monte Carlo simulation and a description of the diffuse astrophysical emission; and iii) including the systematic uncertainties in the rich observational CTA datasets. We find that our spectral and morphological analysis improves the CTA sensitivity by roughly a factor 2. For the hadronic channels, CTA will be able to probe thermal dark matter candidates over a broad range of masses if the systematic uncertainties in the datasets will be controlled better than the percent level. For the leptonic modes, the CTA sensitivity will be well below the thermal value of the annihilation cross-section. In this case, even with larger systematics, thermal dark matter candidates up to masses of a few TeV will be easily studied.Comment: 15 pages, 4 figures, v2: Jfactors for two different DM profiles in Tab.1 added; two new plots added; some clarifications and some references added; results unchanged; matches version published on Phys. Rev.

The Effects of Taxes on Market Responses to Dividend Announcements and Payments: What Can we Learn from the 2003 Dividend Tax Cut?

This paper investigates the effects of capital gains and dividend taxes on excess returns around announcements of dividend increases and ex-dividend days for U.S. corporations. Consistent with standard no-arbitrage conditions, we find that the ex-dividend day premium increased from 2002 to 2004 when the dividend tax rate was cut. Consistent with the signalling theory of dividends, we also find that the excess return for dividend increase announcements went down from 2002 to 2004. However, these findings are very sensitive to the years chosen for the pre-reform control period. Semi-parametric graphical analysis using data since 1962 shows that the relationship between tax rates and ex-day and announcement day premia is very fragile and sensitive to sample period choices. Strong year-to-year fluctuations in the ex-day and announcement day premia greatly reduce statistical power, making it impossible to credibly detect responses even around large tax reforms. The important non-tax factors affecting these premia must therefore be understood before progress can be made in evaluating the role of taxation in market responses.

The flame stability of flat sprays from pressure

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Chemical enrichment of Damped Lyman Alpha systems as a direct constraint on Population III star formation

Damped Ly-alpha absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological lookback times with high precision. Relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly-alpha. Here we study chemical evolution of DLAs using a constrained model for evolution of galaxies and IGM to determine the degree to which DLA abundance measurements can probe Population III enrichment. We find that if the critical metallicity of Population III to II transition is < 10^-4 Zsun, the cosmic Population III SFR is zero for z<8. Nevertheless, at high redshift (z ~ 6) Population III chemical signatures are retained in low-mass galaxies (halo mass < 10^9 Msun). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z ~ 10), and the chemical record of early Population III star formation is retained. We model DLAs as these galaxies by assigning to them a mass-dependent H I absorption cross section and predict distribution of DLA abundance ratios. We find that these distributions are anchored towards abundance ratios set by Population II yields, but exhibit a tail that depends on the Population III IMF for z > 5. Thus, a sample of DLA abundance measurements at high redshift holds the promise to constrain Population III IMF. A sample of just 10 DLAs with relative abundances measured to an accuracy of 0.1 dex is sufficient to constrain the Population III IMF at 4-sigma. These constraints may prove stronger than other probes such as metal-poor stars and individual DLAs. Our results provide a global picture of the cosmic thermal, ionization, and chemical evolution, and can rule out certain Population III scenarios.Comment: 21 pages, 12 figures; this version accepted in Ap