Using an “opaque and secretive network” of subsidiaries in tax havens, top American corporations have stashed $1.4 trillion offshore, a new report from Oxfam shows.With “a range of tricks, tools, and loopholes,” for tax avoidance, the 50 largest U.S. companies, including well-known names like Goldman Sachs, Verizon Communications, Apple, Coca-Cola, IBM, and Chevron, raked in $4 trillion in profits globally …