Rates of Software Engineering Failure

Requirements	Very High
Specification	Low
Design	Low
Implementation	Low
Installation	High
Operation	Enormous
Maintenance	Very High

Requirements

The rate of failure is high for requirements as they are developed by two or more groups of people who come from different disciplines and speak different languages.

Specification,Design,Implementation

These activities are done by a group of simliarly disciplined professionals.

Installation

Installation is often done by people who werent involved in the implementation and dont understand the system.

Operation

Operation is often left to people who dont understand the system or what it is meant to achieve.
Robert Courtney, a New York security consultant, examined thousands of security beaches in both industry and government and found that 68% of them were due to careless operations or incompetent operations.

Maintenance

Maintenance is often done as an afterthought by people who dont understand what they are changing.