Scoring: Burundi

• Date of joining: 1966-11-28 (as updated)
• Expected count from Wikipedia: 11 Prime Ministers (Albin Nyamoya onwards) + 6? Presidents (when Prime Minister abolished)
• Number in Wikidata: 6
• PositionHolderHistory warnings: 0
• Score: 60/170 = 35%

I think the Prime Minister was head of government for much of the time, until the abolition of this position in 1998, but the “office held by head of government” doesn’t reflect this yet, so those officeholders aren’t findable.