100 million Americans on the job

Tomorrow, after being rousted by alarms, clock radios, and spouses' shoves, more Americans than ever before will get out of bed and head for work.

Unemployment has now edged up to 9.5 percent, a post-World War II record. But , for the first time, the government officially reports that the total number of US citizens with jobs has burst past the 100 million mark. From 99.3 million in April, the number of people employed rose to 100.1 million in May.

Much of that increase stems from seasonal factors, caution economists. Newly revised data, however, makes it clear the economy has employed around 100 million Americans since early 1981 - graphic evidence of demographic changes and the job growth wrought by booming technology and service-oriented businesses.

This doesn't mean the percentage of the work force that can't find jobs is about to take a precipitous plunge. The unemployment rate went up 0.1 percent in May from April's 9.4 percent, according to Bureau of Labor Statistics (BLS) figures released last week.

''I don't know anybody who has any grounds for saying (the unemployment rate) will drop rapidly and suddenly,'' Budget director David A. Stockman said at a recent breakfast with reporters.

But it does mean the overall size of the work force keeps getting bigger, as more and more people enter the job market. Total employment rose by 780,000 in May.

The just-released figures must be evaluated cautiously. Newly graduated students flood the job market in May and June. Seasonal adjustment of the employment figures still doesn't really adjust for this influx of the young and eager, warn BLS officials.

''It's kind of embarrassing,'' says John Bregger, chief employment analyst at the BLS.

While there was some growth in total employment last month, says Mr. Bregger, it was probably not as large as the stated 780,000, which is the biggest increase listed by BLS since April 1960.

Combined with a slight increase in the number of hours worked, though, the total job growth figure is reason for being ''cautiously optimistic,'' says Bregger.

It may mean the economy is beginning to stabilize.

''Basically, we've stopped a lot of deterioration in the employment situation ,'' says Paul Groncki, a Citibank economist.

The rise in total employment reflects how the flood of ''baby boomers'' and women into the job market, and the rise of service and electronics industries, have altered the structure of the US economy over the last 20 years.

After readjusting their figures to include 1980 census data, the BLS now says the US first passed the 100 million job mark in February 1981. Last month's 100. 1 million total employment equals a high-water mark first reached in May 1981.

The work force is now roughly double the size of 30 years ago. Much of the increase stems from the postwar baby boom. Most of the 4 million babies a year born from the late 1940s to the early 1960s have now reached adulthood and are looking for work.

Likewise, women have been pouring into the job market. In 1979, for the first time, a majority of women 16 and older held jobs. The rate has continued to increase: 52.1 percent of the working-age female population was employed as of December 1981. The increase in two-income families also has been startling. Both husband and wife now work in more than half of America's families.

Where have all these people found jobs?

''Generally speaking, the services sector of the economy, particularly retail trade, finance, and state and local governments,'' says Bregger of BLS--these have accounted for much of the post-World War II job growth.

Examining where new jobs have come from since 1951 reveals these factors:

* Wholesale and retail trade now employs 21 million workers--more than any other category of the US economy, according to BLS statistics. The sector has grown 112 percent since 1951.

* Manufacturing, the biggest employer 30 years ago, has grown but 20 percent in the intervening years. It is still No. 2 in the job market, with 19 million workers.

* General services, No. 3, has grown the fastest--increasing its work force 239 percent over the past three decades. This category, which includes health care, business services, auto repair, etc., (but not all service-producing industries) now has 18.8 million employees.

* The fourth largest employer is state and local government. Thirteen million Americans, a 30-year increase of 222 percent, now labor for state and local authorities. By contrast, the federal government employs only 2.7 million. Federal employment has grown 18 percent over the same period of time.

As the mix of the work force changes, unforeseen problems and benefits are sure to arise. Some economists, such as Arthur F. Burns, speculate that service industries are more recession-proof than hard-goods manufacturers. During the seven recessions previous to the current downturn, employment in services declined only once.

''The growth of services has been relatively immune to business downturns,'' writes BLS economist Michael Urquhart, though he adds that it's difficult to assess the impact of this on the rest of the economy.

Much postwar job growth has come in relatively low-paying sectors, experts say. A larger percentage of the work force may therefore find themselves stuck in relatively less-attractive positions. And as the recession lingers on into early summer, the unemployment rate appears likely to stay high. For those without a job, a record level of total employment is likely to be of little comfort.

''What we have now is a stubborn, unyielding kind of unemployment,'' says Walter W. Heller, former chairman of the President's Council of Economic Advisers. He says unemployment among black teen-agers has now hit 49.8 percent.