In April 2017, partners from McKinsey & Company sent a confidential final report to the New York City corrections commissioner. They had spent almost three years leading an unusual project for a white-shoe corporate consulting firm like McKinsey: Attempting to stem the tide of inmate brawls, gang slashings and assaults by guards that threatened to overwhelm the jail complex on Rikers Island.

The report recounted that McKinsey had tested its new anti-violence strategy in what the firm called “Restart” housing units at Rikers. The results were striking. Violence had dropped more than 50% in the Restart facilities, the McKinsey partners wrote.

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