"The year 2020 was a bloody one. Murder spiked by 30 percent that year and continued to rise in 2021, abruptly reversing decades of progress on violence in America. One of the most common explanations was that the protests against police brutality in the summer of 2020 had created a hostile environment for police officers, many of whom responded by pulling back from their duties or leaving the force altogether. Officer resignations jumped 35 percent in 2020 and 9 percent in 2021. Then the unexpected happened. Even as police forces across the country continued to shrink, violence began falling fast. According to the crime researcher Jeff Asher, murders fell by 13 percent and violent crime overall by 8 percent in 2023, some of the largest single-year decreases on record—a shift that my colleague David Graham recently called “America’s peace wave.” The improvement, though not universal, was particularly striking in some of the cities that needed it most. Baltimore and Philadelphia each experienced a roughly 25 percent decrease in homicides despite being down about 700 and 1,000 officers, respectively. Detroit experienced its fewest murders since 1966, even though it lost an average of nearly an officer a day for much of 2022. New York City lost more than 2,500 officers in 2023 alone. The murder rate fell there too."