When people complain about "big government," the odds are that they are thinking about the federal sector, but talking about local government.

If federal civilian hiring had kept pace with state and local government employment over the past 30 years, the U.S. government today would have more than 6 million employes, and a civilian payroll in excess of $50 billion.

Instead, the federal government has about 2.6 million full-time workers, excluding military personnel, while state and local government employment now is approaching 13 million.

Back in 1948, after the government employment peak of World War II had receded, the federal government had 1.8 million employes. State and local government had 3.7 million.

In the 30-year period, from 1948 to 1978, federal civilian employment has grown by "only" about 800,000, despite expansions of government programs and responsibilities for everything from air traffic control, weather forecasting drug testing and a higher mail volume.

State and local governments have expanded by 9.3 million workers, primarily to provide more services to the growing suburbs. County governments, which once had several dozen workers, now are the major employers in many areas.

The relative stability of federal employment - much of it made possible by automation - has changed the federal government from an army of clerks to a much higher level (and higher-paid) organization. Today there are said to be more scientists than secretaries in government.

Federal officials believe that the government has reached an almost no-growth position. During the next decade, they foresee the Defense Department (which now employs about half the federal work force) gradually cutting back. Such agencies as HEW, Energy and other service and regulatory bodies are expected to grow gradually.

Pay Lid? The apparent intention of the White House to put a 5 percent to 5.5 percent lid on 1978 federal salaries could be blocked by Congress if it wants to do so.

The law says that federal white collar (and military) pay is to be increased each October. The basis for the increase, called "comparability," is a Labor Department survey of private industry wages. The comparability adjustment is supposed to make government salaries comparable with those in similar jobs in industry.

But the law gives the president great leeway in determing what "comparability" is. It is pretty much what he says it is. If the president decides to shave a "comparability" increase significantly, he must send that plan to Congress. If Congress rejects it, then the comparability raise based on the Labor Department's data goes into effect. If Congress accepts the president's alternative (lower) amount, that action prevails.

If, as expected, President Carter tries to trim the October federal-military pay raises, federal union leaders have promised to take the fight for higher pay to Congress. The problem is that this is an election year.

Voters are worried about inflation, the high cost of government, and "overpaid" politicians. Members of Congress will be getting the same October increase as other federal workers. And it would be difficult for some members to go against an "inflation fighting" program of the president, particularly if it meant voting themselves a pay raise.

Best guess is that if President Carter slaps a lid on federal pay, it will stick. And it also will probably blow his uneasy alliance with the AFL-CIO over the issue of civil service reform.