More than 150,000 federal employees will leave the U.S. government payroll this week after accepting buyouts — the largest single-year exodus of civil servants in nearly 80 years, triggering what unions and governance experts warn is a damaging loss of institutional expertise. The official resignations begin on Tuesday for workers who opted into a deferred exit program that kept them on the payroll through September. The buyouts are a cornerstone of President Donald Trump’s push to shrink the federal workforce, combining financial incentives with threats of dismissal for those who declined the offer. Many left their agencies months ago, according to the federal government's HR office, and have effectively been on paid leave.