Reports on assessment costs

How much does assessment cost? Here are some independent studies that report on the costs spent by engineers around the activity of software assessment:

Victor Basili. Evolving and Packaging Reading Technologies. In Journal Systems and Software 38(1) p. 3—12, 1997.
Quote: 50% effort spent in reading the code
Thomas D. LaToza, Gina Venolia, and Robert DeLine. Maintaining mental models: a study of developer work habits. In ICSE '06: Proceedings of the 28th International Conference on Software Engineering, p. 492—501, ACM. 2006.
Quote: 66% of developers stated that understanding the code is the biggest development problem; 82% stated that it takes a lot of effort to understand the existing code
Andrew J. Ko, Htet Aung, and Brad A. Myers. Eliciting design requirements for maintenance-oriented IDEs: a detailed study of corrective and perfective maintenance tasks. In Proceedings of the 27th international Conference on Software Engineering (ICSE '05). ACM. 126-135. 2005.
Quote: At least 35% effort spent on understanding
Robert L. Glass. Frequently forgotten fundamental facts about software engineering . IEEE Software. Volume 18. Issue 3. 2001.
Quote: Maintenance typically consumes about 40 to 80 percent (60 percent average) of software costs.
Minelli, Roberto and and, Andrea Mocci and Lanza, Michele. Proceedings of the 2015 IEEE 23rd International Conference on Program Comprehension 2015. I Know What You Did Last Summer: An Investigation of How Developers Spend Their Time
Quote: Program understanding is as expected the dominant activity, but as we see our analysis attributes to it even more importance than what the common knowledge suggests, reaching a value of roughly 70%