Ninety-Ninety Rule

n. "The first 90% of the code accounts for the first 90% of the development time. The remaining 10% of the code accounts for the other 90% of the development time." Attributed to Tom Cargill of Bell Labs, and popularized by Jon Bentley's September 1985 "Bumper-Sticker Computer Science" column in "Communications of the ACM". It was there called the "Rule of Credibility", a name which seems not to have stuck.