General Electric, Boeing, 3M, and other US employers with the 100 largest defined-benefit plans will make record pension contributions of $100 billion in 2012, 67% more than two years ago. It may take total contributions of $400 billion from 2011 through 2015 to ease underfunding at the plans, according to consulting firm Milliman. Companies are caught in a vise: The Federal Reserve has said it expects to keep rates at current levels until 2014 means pension plans' fixed-income investments are stagnating just as federal rules shorten the time available to shore up funding. Under the federal Pension Protection Act, which was passed in 2006 and mostly took effect in 2008, tighter accounting rules gave employers seven years to fully fund their retirement plans and required them to use a specified, market-based rate of return to compute liabilities instead of a company estimate.