90–90 Rule

90-90 Rule on Wikipedia

The first 90 percent of the code accounts for the first 90 percent of the development time. The remaining 10 percent of the code accounts for the other 90 percent of the development time.

A wry reinterpretation of the Pareto Principle (or 80-20 rule) that highlights the real-world challenges of completing engineering work. This sentiment is also echoed in Hofstadter's Law.

See also:

• Hofstadter's Law
• The Pareto Principle

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