Several large, urban counties across the United States gained residents or stemmed population declines in the year ending last July. That’s after losing residents in the previous 12-month period amid the COVID-19 pandemic. Population estimates were released Thursday by the U.S. Census Bureau. Population change is driven by migration as people move around inside the country and arrive from abroad. It also depends on whether births outpace deaths, or vice versa. But not every urban center was on the upswing. Los Angeles is the most populous county in the U.S. and it led the nation in population loss last year, declining by 90,000 residents.