Bohem/Basili rules of thumb: IEEE Computer January 2001
Finding and fixing a software problem after delivery is often 100 times more expensive than finding and fixing it during the requirements and design phase
Current software projects spend about 40-50% of their effort on avoidable rework
About 80% of avoidable rework comes from 20 percent of the defects
About 80 percent of the defects come from 20 percent of the modules, and about half the modules are defect free