The bureau used that estimate to adjust the official figures.
The bureau used electronic wiretapping, videotaping and round-the-clock surveillance.
From 2004 to 2009, the bureau used that authority more than 250 times, Mr. Mueller said.
A decade earlier, in the first quarter of 1996, there were slightly fewer than 1,500 jobs in investment banking and securities, a slightly broader definition of jobs that the bureau used then.
The person said the matter was being treated as an assessment, a term the bureau uses to characterize the early stages of an investigation that precede the possible issuance of subpoenas or the use of other investigative tools like wiretaps.
The statistics bureau used a comparison between the FBI count of justifiable homicides by law enforcement and its own count, the arrest-related deaths count, to estimate how far off each count was.
After census takers and census questionnaires were sent out in 2000, the bureau used mathematical formulas to estimate how many members of minorities, renters and others might have been missed in inner cities, rural areas and other places.
Last week, the bureau used $1,000 from the Neediest fund to buy a new full-size bed and mattress, along with sheets and blankets, for Mr. Luo and his wife.
Sean Cunningham, the president and chief executive of the trade group, said the bureau used to publish its research and send it to advertisers, but it had "never been able to keep up with the demand".
Furthermore, the methods the bureau uses are public — and anyone familiar with the data understands that they are "noisy," that especially good (or bad) months will be reported now and then as a simple consequence of statistical randomness.
An official confided that the secret weapon the land bureau used was feng shui, the ancient practice of arranging objects and designing architecture to improve one's health, prosperity and luck.
