More than 100,000 federal employees will receive a special pay boost in January under rules published Tuesday that create 13 new “locality pay” zones and expand most of the existing ones.

In the General Schedule, the pay system for most white-collar executive branch employees, pay varies according to local differences between federal and non-federal pay for comparable jobs, based on Labor Department statistics.

Among the existing localities to be expanded is the Washington-Baltimore zone, which already sprawls out from the District to encompass much of Northern Virginia and Maryland, eastern West Virginia and south-central Pennsylvania.

Counties being added are Dorchester, Kent and Talbot Counties in Maryland, Rappahannock County in Virginia and Franklin County in Pennsylvania. That will benefit nearly 1,100 GS employees, more than 900 of them in Franklin County, according to the Office of Personnel Management.

The General Schedule pay system applies to about 1.5 million federal employees in white-collar occupations below the senior level. There is a separate pay system for blue-collar employees, and still other pay scales for executives and other senior positions.

General Schedule locality pay is based on where the employee works, not where he or she lives, and results in differences in pay for the same job in one location vs. another. Currently there are 31 city areas, plus separate localities for the entirety of both Alaska and Hawaii, and a catchall “rest of the U.S.,” or RUS, locality for other areas.

The notice of the changes says 102,000 employees now in the “RUS” locality would move into one of the new metropolitan areas. Expansion of 21 existing localities will pull about 7,600 more employees into them from that catchall locality, according to the OPM.

Moving from the RUS locality will mean an increase in pay since that is the lowest-paying locality. For example, pay for an employee at the first step of GS-13, commonly an entry-level point for mid-managers, is $83,468 in the RUS locality but $90,823 in the Washington-Baltimore locality. In the highest-paid locality, San Francisco, it’s $98,815.

Since locality pay counts in the calculation of a federal employee’s retirement annuity, the higher pay in turn means an increase in that later benefit.

The pay scales of the new localities are still to be determined. A salary advisory group is to meet in November to receive the latest pay comparison figures–which are based on local salaries, not living costs. That body in turn reports to a higher-level group, and pay scales typically are finalized in late December by an executive order.

Federal employees in general are in line for raises in January 2016 averaging 1.3 percent. That would be paid in two parts: 1 percent to everyone, and the funds for the additional portion parceled out among the localities depending on the pay comparison figures. The result will be raises slightly above 1.3 percent in some areas and slightly below it in others.

The pay council had recommended adding more localities for several years on grounds that the pay gaps in those areas exceed certain thresholds, a process that the rule published in the Federal Register completes. Most of the existing localities were expanded to reflect new data on commuting patterns used in drawing the boundaries.

The closest new locality to the Washington area will be based in Harrisburg, Pa., and will encompass Cumberland, Dauphin, Lancaster, Lebanon and Perry Counties.

Other new localities will be Albany-Schenectady, N.Y.; Albuquerque-Santa Fe-Las Vegas, N.M.; Austin-Round Rock, Tex.; Charlotte-Concord, N.C.-S.C.; Colorado Springs, Colo.; Davenport-Moline, Iowa-Ill.; Harrisburg-Lebanon, Pa.; Kansas City-Overland Park-Kansas City, Mo.-Kan.; Laredo, Tex.; Las Vegas-Henderson, Nev.-Ariz.; Palm Bay-Melbourne-Titusville, Fla.; St. Louis-St. Charles-Farmington, Mo.-Ill.; and Tucson-Nogales, Ariz.