How fast is job growth in the U.S.? There are ways to measure it, using two different sets of official statistics kept by the federal government: by payroll employment and by a survey of households.

Both measures have tended to track together over time. But in the mid-1990s they began to diverge.

• Payroll statistics show more than 1.5 million new jobs created since January.

• But the household survey shows a mere 154,000 people added to job rolls since January.

• Most experts favor the payroll survey since it is based on business records and relies on a larger sample -- but it counts jobs rather than people employed, so its numbers are inflated by people holding two or more jobs.

• The household survey includes such groups as farm workers and the self-employed -- which the payroll statistics do not.

Experts say the payroll survey implies a far lower jobless rate than today's 4.2 percent.

But they also suspect that the household survey has been understating both job growth and labor-force growth in recent years because it misses increases in the population of illegal aliens.

A search for the answer continues.

Source: Gene Koretz, "Solving a Labor Market Enigma," Business Week, November 8, 1999.