How Floruit is Calculated

A person's floruit — their period of professional activity in the book 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), age-at-event records, and the date ranges assigned by the original editors of the London Book Trades index — taking account of annotations such as "(active)" and "(died)" to distinguish professional activity from life events. Events relating to relatives 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 for each.

The start and end dates are graded independently on a scale from A to E:

A

The date comes from a direct record of professional activity: taking on an apprentice, holding a trade address, attending court, holding office in the Stationers' Company, or similar.

B

The date is derived from a life event or editorial attestation: an apprentice binding date plus seven years, a death or burial year, a birth date plus twenty-one years, or a date marked "(active)" in the original editors' index.

C

No individual dated evidence was found. The date is taken from the editors' date range in the original London Book Trades index, without further annotation.

D

No evidence was found for this endpoint, or the original date range was implausibly long and had to be narrowed algorithmically. These dates should be treated with particular caution.

E

A date was computed from the evidence but was then adjusted by a sanity check — for example, an end date that fell after a known death was capped to the death year, or a start date that implied an implausibly young age was moved forward.

Note that some people will have single year floruits, eg, 1761-1761. This is because the source data only has one item with a date and there is no other basis for establishing a broader floruit.