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In this paper we propose a variance estimator for the OLS estimator as well as for nonlin-ear estimators such as logit, probit and GMM. This variance estimator enables cluster-robust inference when there is two-way or multi-way clustering that is non-nested. The variance esti-mator extends the standard cluster-robust variance estimator or sandwich estimator(More)
Forward looking, unconstrained households make child labor and schooling decisions considering their permanent income and weighing the relative returns to child time in various potential activities. The timing of anticipated changes in income should have no effect on child labor and schooling in a setting where households can borrow against permanent(More)
We show the effect of mobile source traffic pollution on infant mortality, both directly and through the channel of airborne particulate matter and carbon monoxide. We show higher levels of local traffic density lead to increased weekly infant mortality rates, and explore variation in effects by distance from traffic source, weather conditions, and infant(More)
We consider statistical inference for regression when data are grouped into clusters , with regression model errors independent across clusters but correlated within clusters. Examples include data on individuals with clustering on village or region or other category such as industry, and state-year dierences-in-diierences studies with clustering on state.(More)
Diagnostic ultrasound contrast agents have been developed for enhancing the echogenicity of blood and for delineating other structures of the body. Approved agents are suspensions of gas bodies (stabilized microbubbles), which have been designed for persistence in the circulation and strong echo return for imaging. The interaction of ultrasound pulses with(More)
T T he Great Recession generated large reductions in employment, earnings, he Great Recession generated large reductions in employment, earnings, and income for workers and families in the United States. The seasonally and income for workers and families in the United States. The seasonally adjusted unemployment rate increased from 5 percent In the more(More)
In this paper we survey methods to control for regression model error that is correlated within groups or clusters, but is uncorrelated across groups or clusters. Then failure to control for the clustering can lead to understatement of standard errors and overstatement of statistical significance, as emphasized most notably in empirical studies by Moulton(More)
Intermittent high intensity ultrasound pulses with circulating contrast agent microbubbles can induce scattered cavitation caused myocardial microlesions of potential value for tissue reduction therapy. Here, computer-aided histological evaluation of the effective treated volume was implemented to optimize ultrasound pulse parameters, exposure duration, and(More)
In this paper we consider inference with paired or dyadic data, such as cross-section and panel data on trade between two countries. Regression models with such data have a complicated pattern of error correlation. For example, errors for US-UK trade may be correlated with those for any other country pair that includes either the US or UK. We consider(More)