Mexicans, who represent the largest and most transformative migration to the United States in modern history, started a gradual return more than a decade ago, with improvements in the Mexican economy and shrinking job opportunities in the United States during the last recession.

But departures have recently accelerated, beginning with crackdowns on immigrants under the Trump administration and continuing under President Biden as many older people decide they have realized their original goals for immigrating and can afford to trade the often-grueling work available to undocumented workers for a slower pace in their home country.

Their departures are one of many factors that have helped keep the total number of undocumented immigrants in the country relatively stable, despite a flood of migrant apprehensions at the southern border that reached two million last year.