Story highlights Reince Priebus served a swift 189 days on the job

The average tenure stretches nearly two and a half years

(CNN) Reince Priebus's six-month stint in the White House landed in the history books on a rainy Friday afternoon: He became the shortest-serving chief of staff. Ever.

No White House chief of staff's term has ended more swiftly than the former GOP chairman's short 189 days on the job.

The widely anticipated announcement followed a series of public attacks on Priebus this week from new White House communications director Anthony Scaramucci , who boarded Air Force One with Trump and Priebus for a Friday afternoon event in New York.

Since the position was first created in 1946, the average tenure of the 29 chiefs of staff stretches nearly two and a half years, according to a CNN analysis of data from a Discovery Channel project called The Presidents' Gatekeepers.

All but seven chiefs of staff have lasted at least one year in the job.