(FORTUNE Magazine) – The big-business job shrinkage continues unabated. IBM is still trying to get rid of some 40,000 employees. GM expects to cut 74,000 at latest count. Just about all defense companies have been cutting furiously. So are hundreds of California-based companies, even utilities like Pacific Bell, now planning to eliminate 11,000 jobs. A recurring theme in news stories about these events is that the organization is doing everything possible to make the cuts voluntary -- to find as many workers as possible who want to leave. A Nexis search turns up 1,868 stories through the first ten months of 1992 in which ''jobs'' appears within 30 words of ''attrition'' or ''buyouts.'' Many large enterprises have been unable to reach their cutback goals via voluntarism, but at least in public, most senior executives remain committed to voluntary programs. Some companies, notably including IBM, continue to talk as though involuntary layoffs represent a failure of management. In mid-October, news stories out of IBM indicated that the company had given divisional executives a nominal right to implement layoffs -- but that anyone executing this new right was in danger of being fired himself, for discrediting the company's full-employment ideal. Seldom seen in print is an opposite view: that cutbacks emphasizing attrition and buyouts are the real management failure. Everyone agrees that, in hiring, companies must routinely try for the best available workers. Why is the logic different in downsizing scenarios? Why should the company suddenly turn passive about who stays and who doesn't? Why not work to retain the best available and push out (i.e., lay off) those who are less valuable (assuming that union contracts make it possible)? The problem goes beyond passivity. Untargeted buyout programs have perverse incentives built into them, especially when the buyouts are available to managerial-professional-technical staffs. In such scenarios, the weak sisters, with limited options elsewhere, can be expected to cling to their jobs, while those with unique talents have every reason to take a package and then go to work elsewhere. Downsizing should represent a unique management opportunity to improve staff quality; in practice, it often does the opposite. A sustaining thought behind the buyout binge is that, by and large, workers are interchangeable -- so why not let them decide who stays? The humane instincts underlying this logic are unfortunately contradicted by an avalanche of data. The data say that workers performing the same jobs at the same companies vary enormously in their productiveness and in their dollar value to the organization. Industrial psychologists John Hunter of Michigan State University and Frank Schmidt of the University of Iowa have exhaustively analyzed many studies measuring workers' value to their companies. Most such studies relate value either to units of output or to the dollar sales attributable to each worker. The basic Hunter-Schmidt finding is that variability among workers is substantial at all levels but increases dramatically with job complexity. In life insurance sales, for example, variability in performance is around six times as great as in routine clerical jobs. ''Individual differences in work output are very large,'' say the authors, adding that better selection methods would do a lot for national productivity -- always assuming that our managers do not then turn around and give the stars incentives to leave.