Software Development: 80% of the contribution comes from 20% of the contributors

• 80% of the engineering is consumed by 20% of the requirements
• 80% of the software cost is consumed by 20% of the components.
• 80% of the errors are caused by 20% of the modules.
• 80% of the software scrap and network is caused by 20% of the errors.
• 80% of the resources are consumed by 20% of the components.
• 80% of the engineering is accomplished by 20% of the tools.
• 80% of the progress is made by 20% of the people.

Source: INDUSTRIAL SOFTWARE METRICS: A TOP-TEN LIST by Barry W. Boehm, TRW Inc.