The world’s biggest pension fund posted the biggest quarterly gain in its history as Japanese stocks surged and a plunge in the yen boosted overseas investments since Election Day. The Government Pension Investment Fund returned 8 percent in the three months ended Dec. 31, increasing assets to 144.8 trillion yen. The United States’ dwindling labor federations and defenders of America’s workers are taking a page from corporate America: firing some of their own employees. The AFL-CIO confirmed that it will dismiss “several dozens” of the roughly 400 staff and furlough others working at its headquarters just north of Lafayette Square in Washington. Earlier, in December, the separate Service Employees International Union warned employees that it “must plan for a 30 percent reduction” in its budget by Jan. 1, 2018.