The answer depends on which survey you are reading
If one person holds two jobs at the same time, are they one employed person or two jobs in the U.S. employment data? Both answers can be correct because the monthly jobs report uses the CES establishment survey and the CPS household survey.
CES primarily measures nonfarm payroll jobs, while CPS primarily measures people's labor-force status. The same worker is therefore handled differently in the two systems.
In CES, jobs at different establishments can be counted separately
The CES establishment survey is based on payroll records from businesses and government agencies. If someone works at establishment A during the day and establishment B at night and appears on both payrolls, the worker is counted at each establishment.
BLS also specifies that a person performing different jobs at the same business establishment is counted once. The important distinction is therefore not simply the number of job titles a person has, but whether the person appears on payrolls at separate establishments.
In CPS, the same employed person is counted once
The CPS household survey asks whether a person is employed. If someone meets the employment definition during the reference week, that person is counted once in total employment whether they have one job, two jobs or more.
CPS separately measures multiple jobholding, so analysts can still track how many employed people have more than one job. But that does not cause a multiple jobholder to be counted several times in the headline number of employed people.
100,000 payroll jobs added does not mean 100,000 newly employed people
This is why a gain of 100,000 nonfarm payroll jobs should not automatically be translated into “100,000 people found jobs.” The payroll figure measures the net change in payroll jobs. If some new jobs are second jobs taken by people who were already employed, payroll growth can exceed the increase in employed people.
The reverse is also possible. If a person with two jobs loses one but keeps the other, CES can record one fewer payroll job while CPS still classifies that person as employed.
How can multiple jobholding widen the gap between the surveys?
If second jobs and part-time jobs become more common, payroll jobs can continue rising while the household survey's number of employed people grows more slowly. This does not make the payroll figure meaningless; it simply measures a different dimension of the labor market.
Job growth should also be checked across industries. If most new payroll jobs are concentrated in only a few sectors, the labor-market picture may differ from one in which hiring is broad-based. See Are Non-Farm Payrolls Still Strong When Job Gains Are Concentrated in Few Sectors?
Why the distinction matters when reading nonfarm payrolls
Mixing up jobs and people can lead to incorrect conclusions. Strong payroll growth does not, by itself, prove that household employment increased by the same amount. Likewise, a change in household employment is not a substitute for the payroll-jobs measure.
One of the first questions to ask when reading a labor-market statistic is therefore: does this number count jobs or people? CES counts payroll employment by establishment, so one person can be represented more than once when working at separate establishments. CPS total employment is person-based, so the same individual is counted once.
Identify the statistical unit before judging the labor market
The headline numbers may look simple, but the statistical unit determines what they actually mean. Payroll jobs are useful for tracking how many paid positions businesses maintain and which industries are adding employment. Household employment is better suited to answering how many people are working.
Once the treatment of multiple jobholders in CES and CPS is clear, it becomes much easier to understand why strong nonfarm payroll growth does not necessarily mean the same number of people have just entered employment.