A retailer that adds temporary workers every holiday season may report more employment in November and December, then fewer workers after the rush. Those predictable swings can obscure whether hiring is strengthening or weakening underneath. Seasonal adjustment estimates recurring patterns like these and accounts for them in monthly labor statistics. It helps readers compare one month with another on a more even basis, but it does not erase the survey’s timing, turn an estimate into a complete count, or change who qualifies as unemployed.Bureau of Labor Statistics
The calendar can overwhelm the signal
Many industries experience regular changes tied to seasons, holidays, weather or production schedules. Retailers may staff up for holiday shopping; some outdoor work follows warmer weather; schools and factories can follow recurring calendars. A raw monthly employment figure combines these expected movements with changes that may reflect a shift in labor demand. If every holiday season brings a similar hiring surge, the raw increase alone does not show whether the labor market is unusually strong that year.
Seasonal adjustment is a statistical way to account for recurring patterns. BLS publishes seasonally adjusted measures, and the adjustment is intended to make comparisons across adjacent months more informative. It does not mean that seasonal jobs are excluded or that a worker’s job is somehow reclassified. The underlying observations still come from the relevant survey and reference period; the adjustment changes how the published series accounts for predictable calendar effects.Bureau of Labor Statistics
A hypothetical retailer illustrates the difference
Imagine, hypothetically, a retailer that adds 100 workers each November as it prepares for a recurring holiday rush, then sheds about the same number after the season. If this year’s raw November employment increase is close to that usual pattern, a seasonally adjusted series would account for the recurring lift. If the increase is larger or smaller than the pattern the adjustment expects, some of that difference can remain visible in the adjusted figure. These invented numbers illustrate the idea, not an official estimate.
The adjustment therefore does not simply subtract every seasonal job from the economy. It estimates how much of a movement is typical for that time of year, so readers can better see departures from the pattern. A seasonal worker remains a worker in the underlying data. The adjusted figure helps answer a different question: how does this month compare after recurring calendar movements have been taken into account?
The reference period still matters
The BLS household survey classifies people according to their activities during a reference week, usually the week that includes the 12th of the month. The unemployment rate is based on the civilian labor force: people who are employed and those who are jobless, actively seeking work, and available for work. A person who has no job but has not actively looked during the preceding four weeks generally is not counted as unemployed under that definition.Bureau of Labor Statistics
That timing can matter to interpretation. A seasonal worker hired after the survey reference week may not appear as employed in that month’s household survey response, even if the person is working later in the month. A seasonal adjustment cannot move the reference week or resolve every mismatch between a recurring hiring calendar and a survey window. Readers should check which month the measure covers and what it counts before comparing it with a personal impression or another series.
Compare like with like
For a short-term month-to-month comparison, a seasonally adjusted series is usually the relevant view because it accounts for recurring patterns. A year-over-year comparison can also help readers see a month against the same month in an earlier year, though that does not remove every difference between periods. The right comparison depends on the question: a recurring holiday bump looks different when compared with the prior month than when compared with the same season last year.
The September 2026 employment report, for example, said payroll employment rose by 29,000 and the unemployment rate was 4.2 percent; the report also identified its household and establishment survey measures as seasonally adjusted.Bureau of Labor Statistics Those figures describe September, not October, and they are estimates from different surveys with different coverage. Seasonal adjustment makes monthly comparisons more usable, but it does not establish why a number changed or how any one worker’s experience fits the national pattern.
Sources & further reading
- How the government measures unemployment ↗Bureau of Labor Statistics
- September 2026 employment report ↗Bureau of Labor Statistics
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