Must-read: David Card and Laura Giuliano: “Can Tracking Raise the Test Scores of High-Ability Minority Students?”

Must-Read: David Card and Laura Giuliano: Can Tracking Raise the Test Scores of High-Ability Minority Students?: “We study the impacts of a tracking program in a large urban school district that establishes separate “gifted/high achiever” (GHA) classrooms…

…for fourth and fifth graders whenever there is at least one gifted student in a school-wide cohort. Since most schools have only a handful of gifted students per cohort, the majority of seats are filled by high achievers ranked by their scores in the previous year’s statewide tests…. Participation in a GHA class leads to significant achievement gains for non-gifted participants, concentrated among black and Hispanic students, who gain 0.5 standard deviation units in fourth grade reading and math scores, with persistent effects to at least sixth grade. Importantly, we find no evidence of spillovers on non-participants. We also investigate a variety of channels that can explain these effects, including teacher quality and peer effects, but conclude that these features explain only a small fraction (10%) of the test score gains of minority participants in GHA classes. Instead we attribute the effects to a combination of factors like teacher expectations and negative peer pressure that lead high-ability minority students to under-perform in regular classes but are reduced in a GHA classroom environment.

Must-Read: Rajiv Sethi: Threats Perceived When There Are None

Must-Read: Mark Thoma sends us to Rajiv Sethi, who makes a convincing case that the very sharp Sendhil Mullainathan has gotten one wrong here:

Rajiv Sethi: Threats Perceived When There Are None: “He argues that ‘eliminating the biases of all police officers would do little…

…to materially reduce the total number of African-American killings…. 28.9 percent of arrestees were African-American… not very different from the 31.8 percent of police-shooting victims…. If police discrimination were a big factor in the actual killings, we would have expected a larger gap between the arrest rate and the police-killing rate….
 
A key assumption… is that encounters involving genuine (as opposed to perceived) threats to officer safety arise with equal frequency across groups…. A safe encounter might well be perceived as risky, as the following example of a traffic stop for a seat belt violation in South Carolina…. Sendhil is implicitly assuming that a white motorist who behaved in exactly the same manner as Levar Jones did in the above video would have been treated in… the same manner by the officer…. Think of the encounter involving Henry Louis Gates and Officer James Crowley back in 2009… a safe encounter… [that] may not have happened in the first place had Gates been white. If the very high incidence of encounters between police and black men is due… to encounters that ought not to have… a disproportionate share… will be safe, and one ought to expect fewer killings per encounter in the [presence of bias toward having an encounter and the] absence of bias [once the encounter begins]. Observing parity would then be suggestive of bias…. In justifying the termination of the officer in the video above, the director of the South Carolina Department of Public Safety stated that he ‘reacted to a perceived threat where there was none.’  Fear is a powerful motivator… even when there are strong incentives not to shoot…

Astonishing Imprint of the Pattern of Racial Housing Segregation on Jogging Routes in Kansas City…

Joseph Stromberg: This interactive map shows the most popular running and cycling routes in your city: “Strava, a popular app used to log routes and times for cyclists and runners…

…has an an interactive heatmap of 77 million rides and 19 million runs recorded by users over the past few years. It is made up of more than 220 billion total data points, and it is amazing…

Strava Global Heatmap

Terrifying rather than amazing, I would say…