Although most white-collar federal workers will get an automatic 4.8 percent raise next month, the guaranteed increase for most of the 130,000 middle-management employes being shifted to a new GM job title will be only 2.4 percent.

The 130,000 people -- perhaps as many as 40,000 of them in metropolitan Washington -- are all Grade 13, 14 and 15 career workers who are going under a merit pay system created by former president Jimmy Carter's Civil Service Reform Act.

Under merit pay, those GS 13-15 people designated by their agencies as supervisors or managers -- hence the GM prefix -- are guaranteed only one half of the October percentage pay raise that their Grade 1 through 12 subordinates get.

To get more, and the majority are expected to get more, they must meet criteria established by their own agencies and bosses' rating them as fully satisfactory, exceptional or outstanding in performance for the year. (Designations vary by agency but most are using a five-tier ranking system.) Workers who get rated as minimally satisfactory or unsatisfactory would naturally get the smallest 2.4 percent raise, or none at all.

Amounts of the merit pay increases will differ from agency to agency. Because each agency will have a fixed amount of merit pay funds to finance raises for GM personnel, agencies that give out relatively big raises to large groups of managers/supervisors, will have to cut back on the amounts given to those rated lower.

Money for merit pay will come from amounts that would normally be designated for the full amount of the pay raise (4.8 percent this year) plus money that would have been used to give quality step increases and longevity pay raises to those workers.

Persons under the GM category will no longer get automatic within-grade raises, which are worth about 3 percent and go to other workers who get "satisfactory" ratings every one, two or three years, depending on their time in grade.

Many people who are going into the GM merit pay system this year are nervous about its application -- will raises be based on merit or favoritism? -- and officials who must dole out raises are worried about the paperwork and the time involved in making the merit pay decisions, not to mention their impact on workers. A few agencies went under merit pay last year. But for most supervisors/managers the fun begins in a few weeks.

Some agencies will decide in time to give workers whatever raises they will get with their October paychecks. Others will give employes only the 2.4 percent raise (half the regular increase) and then later on make retroactive payments to persons due more.