# Birthday month derivation

Indicates how the month of birth was sourced (e.g., individual-level declaration vs household-level inference).

- API name: `birthday_month_derivation`
- Category: Life event
- Type · unit: Text
- Individuals with a value: 235.1M (91.3%)
- Latest collection: Jun 1, 2026, refreshed every two months
- How values combine: Read from a single source field.

## Links

- [Catalog page](/catalog/v2/birthday_month_derivation)
- [Published statistics (JSON)](https://static.faraday.ai/figv2/birthday_month_derivation.json)
- [API reference](/docs/reference/getattribute)