This paper focuses on the clients' impact on estimation accuracy in software development projects. Client related factors contributing to effort overruns as well as factors preventing overruns are investigated. Based on a literature review and a survey of 300 software professionals we find that: 1) Software professionals perceive that clients impact estimation accuracy. Changed and new requirements are perceived as the clients' most frequent contribution to overruns, while overruns are prevented by the availability of competent clients and capable decision makers. 2) Survey results should not be used in estimation accuracy improvement initiatives without further analysis. Surveys typically identify directly observable and project specific causes for overruns, while substantial improvement is only possible when the underlying causes are understood.

Our Assessment: Grimstad et al. reviewed 8 studies that surveyed opinions about the impact of clients on estimation accuracy and also reported a survey they undertook of the opinions of 300 software professionals. The positive and negative factors they found in their survey were similar to those found in previous studies.