The Trended Workers data source is specifically designed for reports that display trends over time, such as headcount, turnover, and demographics. It captures periodic snapshots of worker data (monthly, quarterly, etc.), which allows organizations to track workforce metrics historically.
From the Workday binder: "Trended Workers captures snapshots of worker data at periodic intervals, providing historical reporting across time dimensions. This enables reporting on headcount, attrition, and demographics in a time series format." By contrast, Workers for HCM Reporting is used for current-state data, not trending. Worker History provides effective-dated transaction-level history but does not automatically generate trending snapshots. Headcount is a standard delivered report and not a reusable data source for custom trending analysis.
Therefore, the most appropriate data source for worker headcount trends over time is A. Trended Workers.