They call him Mr. Census, this slight, dapper man who has spent nearly 40 years turning statistics into history.

But David Kaplan takes a more modest view of his career at the U.S. Census Bureau, which began in 1940 as a $28-a-week clerk and ended last week when he retired from a $47,500-a-year job as assistant director for demographic censuses -- coordinating the 10-year census.

"I'm just a civil servant," shrugged 60-year-old Kaplan. "I feel strongly that the taxpayer is paying our way, and we should be as honest and competent as possible."

Last week, more than 200 of Kaplan's coworkers gathered to honor him at a retirement party at Bolling Air Force Base. Their tributes portrayed a dedicated man known for carrying home bulging briefcases, galloping down halls to arrive at meetings on tme and lunching quickly on a cheese sandwich from the local drugstore or cottage cheese from the employe cafeteria.

"Dave Kaplan's retirement marks the end of an era," noted Ross Eckler, former director of the bureau. "The Great Depression was an enormous recruiting source for us, and Dave was one of the few remaining members of what we call the fabulous class of 1940."

In 1940, with a BA in statistics from New York University and one suitcase, 22-year-old Kaplan made the longest trip he'd ever taken in his life when he moved to Washington to join the thousands of workers compiling data for the 1940 census.

Kaplan was paid $3.65 a day to alphabetize birth record cards. Although the work was often tedious, he was proud to work for an organization he considered "the statistical capital of the world."

"I've often wondered how pure chance played a part in my career," Kaplan recalled. "When we were all lined up to begin work that first day, some of us were told to turn left and work on population statistics, and some of us were told to go right and work on agriculture. Those who worked on agriculture didn't have the opportunities we did in population and didn't last at the bureau."

In six months he became a supervisor, directing 20 clerks who turned census interviews into numbers for tabulation. Several months later he moved to the occupational statistics section, where he developed tables used to analyze employment data.

He rose through the ranks gradually, becoming head of the occupation statistics division for the 1950 census and assistant chief of the population division in the early 1960s.

During tha time he married and moved into a modest housing development in Silver Spring where several other Census Bureau employes lived. There he began a carpooling routine with other residents of "Census City," a routine he never varied until his retirement.

By the time he was appointed coordinator of the 1970 census, Kaplan had worked throughout the bureau -- developing questionnaires, organizaing research programs, balancing budgets and tabulating responses.

"The census is a very complex business that entails thousands of details and results in hundreds of documents," said Kaplan, who coordinated the work of more than 200,000 people in 400 field offices for the 1970 census, which cost $200 million.

"We have to recruit, train and maintain an army, and then demobilize the army in a six-month period," Kaplan said.

"There's a peculiar thing about census work -- essentially you work 10 years for one day. I spent 10 years of my life looking to Paril 1, 1970 -- the day people were to mail in their returns.

"For years, I knew that day was going to be a Tuesday, and I kind of expected the sun to rise differently on that day. I'd go down the street and see people carrying Census envelopes to the mailbox, and that's a big thrill."

The bureau was quiet that day, "like being in the eye of a storm," Kaplan said. But the week before things were hectic.

"The forms were to be delivered on March 28, and during that week the Post Office went on strike," Kaplan grimaced, his bird-like frame shuddering at the memory. "I was alost hysterical. Fortunately, the strike petered out by the end of the week, and 87 percent of the households returned their forms. Those who didn't were visited by a census taker."

Kaplan submitted the results ofthe 1970 census to the President on Jan. 1, 1971, as required by law. The figures are used for Congressional reapportionment and scores of government, business and academic purposes. By June 1973, roughly 2,000 census reports had been compiled. Kaplan received the Department of Commerce Gold Medal, the department's highest award, for his work.

In the midst of preparations for the 1980 census and the new, mid-decade census in 1985, Kaplan decided to retire.

"It's like cutting an umbilical cord," confessed Kaplan, who plans to do some consulting work and work on his hobby of making stained glass. "But there comes a time when you look at your personal calendar and figure it's time to stop.

"I do have a tremendous feeling of accomplishment, something like writing the history of a country. It's a kick to go into the library and see books you've helped to write."

Some of his coworkers, however, are not joyful about Kaplan's retirement.

"It will be difficult to think of conducting a census without Dave Kaplan, because he gave the census personality and animation," bureau director Manuel Plotkin told the crowd at Kaplan's retirement party. "He ran the census like a mom-and-pop grocery store -- you'd think it was his own money he was spending."

"Dave had the ability to hold a one-inch document of single-spaced charts to his forehead and tell you on what page you fouled up," added Sheldon Rubin, one of Kaplan's assistants.

But some colleagues will remember Kaplan for more than his statistical capabilities.

"He's a man who doesn't forget you," said statistical assistant Minnetta Miller. "Despite his busy schedule, when I was going in for heart surgery he found time to ome and wish me well."

After an emotion-choked speech, Kaplan advised his colleagues not to worry about his retirement years.

"Old statisticians never die," he grinned. "They just stop figuring."