GlossaryStatistics and interpretation
Call volume
Call volume counts contacts or dispatch events under stated rules. Learn why it differs from incident totals, unique callers, and responding units.
Call volume is the number of calls or dispatch events counted during a stated period under a source's rules. The label needs a counting unit: telephone contacts, requests for service, and dispatched incidents can produce different totals. A call-volume figure does not automatically measure crimes, patients, or responding vehicles.
What is being counted
One emergency can generate several telephone calls. Dispatchers may connect those contacts to one incident, while several units respond to that incident. Each stage produces a useful measure, but the measures answer different questions.
San Francisco's dispatched-call documentation explicitly distinguishes unique dispatch identifiers from incoming 911 contacts. It also includes officer-initiated activity. This is a documented local counting model, not a definition that every agency follows. DataSF dispatched-call explainer.
Example
Hypothetical example: Three residents telephone about the same blocked roadway. The dispatch center links all three contacts to one event and assigns two units. A report counting incoming contacts records three; a report counting distinct dispatched events records one; a unit-response report records two assignments, assuming both meet its inclusion rules.
None of those totals is inherently incorrect. Calling all three “call volume” without identifying their units would make them look contradictory and could misstate how much activity changed.
Common confusion
A call is not a confirmed offense. Requests can concern assistance, suspicious circumstances, traffic, or conditions that turn out differently from the initial description. Officer-initiated checks may also appear alongside public requests.
Call volume is not the number of residents seeking help. One person can make several contacts, and several people can report one event. A count of calls therefore cannot establish a count of unique people without additional information and a suitable method.
Comparing workload over time
Check whether the release includes all recorded calls, only dispatched events, or only closed events. Identify the date field and whether canceled calls, duplicate entries, transfers, and activity initiated by personnel are included.
Keep these choices consistent across periods. If an agency begins publishing a previously excluded category, the higher published total may partly reflect broader coverage. Volume also leaves out duration and resources: two periods with the same number of events can involve very different commitments of personnel and time.