In Saturday's Business section, a credit line was inadvertently omitted from a chart showing employment in manufacturing and service industries. The source of the data was Wharton Econometric Forecasting Associates.

The nation's unemployment rate remained unchanged last month at 7.3 percent, but the share of the working-age population with jobs reached the highest level ever recorded, the Labor Department reported yesterday.

Civilian employment increased by 430,000 in March to a total of 107.1 million, some 60.3 percent of the non-institutional population aged 16 or over.

If the men and women in the armed forces are included, the figure is 60.7 percent. Not quite 72 percent of all working-age men had jobs last month, as did just over half of the women.

Overall, the economic expansion of the past year has added 3 million jobs. But because of unusually strong growth of the civilian labor force, the number of unemployed workers has dropped only from 8.8 million to 8.4 million, the department said, which accounts for the relatively small decline in the unemployment rate from 7.8 percent in March, 1984,to the current 7.3 percent.

In addition, the uneven nature of the expansion continues. Janet L. Norwood, commissioner of labor statistics, noted that most of the job growth has occurred in services, retail trade and construction, with the latter reaching a record level of 4.6 million last month.

"Manufacturing employment, by contrast, at 19.7 million in March, has shown no growth since last August," Norwood told the Joint Economic Committee.

"Within manufacturing, several industries -- lumber and wood products, furniture, electrical and electronic equipment, instruments, automobiles, rubber and plastics, and printing and publishing -- have more than regained the number of jobs lost during the recession in the 28 months of recovery.

"Auto employment has declined in the past two months, however," she continued, adding, "Four industries -- steel, textiles, petroleum, and leather -- have continued to lose jobs even during the recovery."

Most analysts attribute the sharp divergence in employment trends to increased foreign competition. The industries competing against imported goods are in many cases struggling, while those not facing such competition, such as construction, retailing, restaurants and business services, are doing well.

With consumer confidence high and business spending on new plants and equipment strong, most forecasters predict that the economy will continue to grow at anywhere from a 2.5 percent to 4 percent annual rate this year. Whether the unemployment rate declines may be determined by where the growth rate falls within that range.

For instance, George Perry of the Brookings Institution expects the gross national product, adjusted for inflation, to go up at an average rate of 3.5 percent for the next three quarters -- and the unemployment rate to drop to 7 percent by the third quarter. Wharton Econometric Forecasting Associates, on the other hand, is looking for average growth of just under 3 percent and little if any drop in the unemployment rate.

"The bad news," said Wharton's summary of its latest forecast, "is that this robust domestic demand for goods is increasingly being satisfied by foreign sources.

This is showing up not only in the almost inexorable deterioration in the trade statistics but also in industrial production and capacity utilization . . . As a result of this import penetration, the manufacturing sector of the U.S. economy is suffering."

The March figures from the Labor Department indicate that particularly bad weather during the week in which the employment survey was taken in February did, as many analysts had thought, affect that month's results.

This was especially evident in the length of the average workweek in manufacturing, which bounced back from 39.9 to 40.4 hours. However, the March level was still 0.2 hours below the January figure and 0.3 hours less than that of a year ago.

The department reported that the unemployment rate for adult men fell from 6.3 percent in February to 6.2 percent last month. The rate for adult women was unchanged at 6.7 percent. That for teenagers dropped from 18.4 percent to 18.2 percent.

Unemployment among blacks fell from 16.3 percent to 15.2 percent, but it remained slightly higher than it was in the November to January period.

The rate of joblessness among workers of Hispanic origin rose from 9.7 percent to 10.2 percent, but that rate was lower than it was in the last quarter of 1984 and in January.

An alternate measure of unemployment that includes the nation's military forces stationed in the United States also was unchanged in March at 7.2 percent.

In its quarterly report on why persons of working age are not either employed or seeking work, the department said 56.8 million said they do not want a job now for reasons such as being retired, ill, in school or keeping house. Another 5.8 million persons said they would like a job but are not looking. Some of that group also are not looking because they are ill, disabled, in school or have home responsibilities.

However, 1,253,000 persons said they would like a job but are not looking because they think they cannot get a job. Even though employment has gone up sharply since the first quarter of last year, the number of these so-called discouraged workers has declined by slightly less than 100,000 during that time.

The department, in another part of its report, said that its index of hourly earnings rose 0.4 percent in March, leaving the index 3.3 percent higher than it was a year earlier. Information about inflation is not yet available for last month, but in the 12 months ended in February, the real value of the index fell 0.4 percent. In other words, hourly earnings adjusted for inflation went down.