Reproduced from a Pew Research Center study; Chart: Axios VisualsMexicans no longer make up the majority of unauthorized immigrants in the U.S. — a significant change from the early 2000s — as more are leaving than arriving, according to a new study by the Pew Research Center. The big picture: The immigrant population in the U.S., which has its smallest unauthorized immigrant population in more than a decade, is markedly shifting. There are fewer new unauthorized immigrants now. The majority — 66% — have been in the U.S. for at least a decade. In 2000, unauthorized immigrants were more likely to have been in the U.S. for fewer than 5 years than over 10. Between the lines: The change isn't because border enforcement has improved. Mexicans simply aren't attempting to cross the border as often as they used to. In 2000, 98% of all border patrol arrests were of Mexican nationals. Last year, Mexicans made up just 38% of border arrests, according to Customs and Border Patrol data.Meanwhile, there's been a surge of migrants from Central American countries, like Guatemala, El Salvador and Honduras.And the share of both legal and unauthorized immigrants from Asian nations has continued to grow. Go deeper ... Chart: How immigration levels in the U.S. have changed since 1900