Ask three providers how many software engineering roles are open in Germany and you will get three answers that are not close. The gap is almost never dishonesty. It is definitions.
The five choices that produce the gap
- Deduplication. Counting listings rather than roles inflates a market by however much cross-posting happens in it — which varies by country and by seniority.
- Expiry. A provider that removes a listing the day it disappears reports fewer roles than one that keeps it for thirty days. Both are defensible; only one is comparable to a vacancy statistic.
- Multi-seat requisitions. One requisition for six seats is one or six depending on the rule.
- Agency listings. Include them and the count rises; the same underlying role may be advertised by an employer and two agencies.
- Source mix. A careers-page index and a board index cover different employers. Neither is a superset.
What to ask before comparing
- Are you counting listings or roles?
- When a listing disappears from the source, how long until it leaves your count?
- Do you include agency-sourced postings, and can I exclude them?
- What is your source mix — careers systems, boards, or a purchased feed?
A provider who cannot answer these has not decided, which means their number drifts as their pipeline changes.
The practical advice
Do not mix sources in one series. A chart that switches provider halfway will show a step change that looks like a labour market event and is a definitional artefact. Pick one, understand its rules, and treat the absolute level as less trustworthy than the direction.
And about official statistics
Government vacancy series count differently again — usually seats, from employer surveys, with a lag of weeks. Job posting data is faster and broader; official series are slower and more consistent. They answer different questions and the gap between them is not an error in either.