A lthough many countries use high-stakes testing to rank students for college admission, the consequences of this policy are largely unknown. Does having a particularly good or bad performance on a high-stakes examination have long-term consequences for test takers, after accounting for a student's cognitive ability? Cognitive acuity can be affected temporarily by a variety of factors, including the intake of caffeine, nicotine, sleep deprivation, and noise (Jarvis 1993;Angus, Heslegrave, and Myles 1985;and Goriounova and Mansvelder 2012). Insofar as there are permanent consequences to variation induced by completely random shocks to student performance, it suggests that the use of high-stakes testing as a primary method for ranking students may be unfair. Furthermore, aggregate welfare may be reduced by relying too heavily on examinations that provide noisy measures

Cognitive performance is critical to productivity in many occupations and potentially linked to pollution exposure. We evaluate this potentially important relationship by estimating the effect of pollution exposure on standardized test scores among Israeli high school high-stakes tests (2000)(2001)(2002). Since students take multiple exams on multiple days in the same location after each grade, we can adopt a fixed effects strategy estimating models with city, school, and student fixed effects. We focus on fine particulate matter (PM 2.5 ) and carbon monoxide (CO), which are considered to be two of the most dangerous forms of air pollution. We find that while PM 2.5 and CO levels are only weakly correlated with each other, both exhibit a robust negative relationship with test scores. We also find that PM 2.5 , which is thought to be particularly damaging for asthmatics, has a larger negative impact on groups with higher rates of asthma. For CO, which affects neurological functioning, the effect is more homogenous across demographic groups. Furthermore, we find that exposure to either pollutant is associated with a significant decline in the probability of not receiving a Bagrut certificate, which is required for college entrance in Israel. The results suggest that the gain from improving air quality may be underestimated by a narrow focus on health impacts. Insofar as air pollution may lead to reduced cognitive performance, the consequences of pollution may be relevant for a variety of everyday activities that require mental acuity. Moreover, by temporarily lowering the productivity of human capital, high pollution levels lead to allocative inefficiency as students with lower human capital are assigned a higher rank than their more qualified peers. This may lead to inefficient allocation of workers across occupations, and possibly a less productive workforce.

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This paper revisits the debate around the link between population density and the severity of COVID-19 spread in the USA. We do so by conducting an empirical analysis based on graphical evidence, regression analysis and instrumental variable strategies borrowed from the agglomeration literature. Studying the period between the start of the epidemic and the beginning of the vaccination campaign at the end of 2020, we find that the cross-sectional relationship between density and COVID-19 deaths changed as the year evolved. Initially, denser counties experienced more COVID-19 deaths. Yet, by December, the relationship between COVID deaths and urban density was completely flat. This is consistent with evidence indicating density affected the timing of the outbreak—with denser locations more likely to have an early outbreak—yet had no influence on time-adjusted COVID-19 cases and deaths. Using data from Google, Facebook, the US Census and other sources, we investigate potential mechanisms behind these findings.

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