ByMichael A. Verespej The weakening of corporate pension plans over the next 10 to 20 years will present a major threat to the economy, suggests Jerome M. Rosow, chairman and CEO of the Work in America Institute Inc. The reason: an aging society. People between the ages of 45 and 64 will be the fastest-growing age group in the next decade and that, he suggests, will make pension policy -- and good pensions -- increasingly important. If employers continue the recent trend of targeting pension plans as a way to reduce costs and provide a short-term or intermediate-term boost to the bottom line, which could lead to government intervention, lawsuits, and organized hostility from employees. "Employers [should] reevaluate pension policy" taking into consideration "the long-term interests of their core workforce," says Rosow.