How Floruit is Calculated

A person's floruit — their period of professional activity in their chosen trades — is computed algorithmically from dated evidence across the database. The algorithm draws on records of apprentice bindings and freedoms, addresses, court appearances, Stationers' Company offices held, and entries in the masters table. Where direct professional evidence is unavailable, it falls back to life dates (birth, death, baptism, burial) and age-at-event records to estimate a plausible working life, and as a last resort uses the date ranges assigned by the original editors of the London Book Trades index. Events relating to relatives (e.g. "son — Patrimony") are excluded, evidence dated after a person's death is discarded, and statistical outlier detection removes stray dates that fall far outside the main cluster of activity. The result is a start year, an end year, and a confidence grade from A to E.

A

Both the start and end dates are supported by direct records of professional activity: taking on apprentices, holding a trade address, attending court, holding office in the Stationers' Company, or similar.

B

At least one of the start or end dates comes from direct professional records; the other is derived from life events such as apprentice binding, freedom, death, or birth dates.

C

No direct professional records were found. Both dates are derived from life events — for example, a floruit start estimated from a binding date plus seven years of apprenticeship, or an end date taken from a death or burial record.

D

No individual dated evidence was found in the database. The floruit is based on the date range assigned by the original editors of the London Book Trades index.

E

Evidence was limited or conflicting. Only one endpoint could be determined, or the raw evidence produced an implausibly long span that had to be narrowed. These dates should be treated with caution.