The murder wave that swept over big cities and small towns since the beginning of the pandemic continued across the United States through 2021, according to crime data. But Dallas, the nation’s 9th largest city, bucked the trend. In Los Angeles, murders jumped 12 percent compared to 2020. Chicago saw more than 800 murders in 2021, the highest in 25 years. Philadelphia logged 559 homicides, the highest on record. In Dallas, murders dropped by 12 percent. The murders are part of a broader overall drop in crime in Dallas. Robberies dropped by 27 percent and aggravated assault by 2 percent—making Dallas one of few major cities that saw a reduction in violent crime during 2021. The city has about 3,100 police officers serving 1.3 million residents. Back in May 2021, Dallas’ violent crime was on track to surpass that of 2020, as happened in other cities. But that very month …