Defined benefits plans
are unreasonable. Basically, whether it's defined benefit or defined contribution, the company has to take the salary contributions of its employees and put them in a pension fund, which is then invested in such a way as to pay out the benefits in perpetuity. The differences with defined benefits are 1.) if you die soon after retirement, your family gets shafted (your benefit/contribution ration makes assumptions about your lifetime) and 2.) if the market fails, the company gets screwed.
Sure, the company with a defined-benefits pension fund which got wiped out by a market crash could have invested in very conservative funds with low volatility, but those also get low returns, so more of the employees salary would have to be siphoned off into the pension fund. Isn't it better to give the employees a choice of what to invest in? Whether to accept low returns for low risk, or to take bigger risks for bigger returns? Basically, there are companies which are supposed to know how to turn defined contributiosn into defined benefits - we call them mutual funds. If they screw up, at least they don't take innocent employees' jobs with them when they fail. Why should a company like IBM be forced to be involved in that business?