Aug 042009
Case studies were conducted with three development teams at Microsoft and one at IBM that have adopted TDD. The results of the case studies indicate that the pre-release defect density of the four products decreased between 40% and 90% relative to similar projects that did not use the TDD practice. Subjectively, the teams experienced a 15–35% increase in initial development time after adopting TDD.
http://www.springerlink.com/content/q91566748q234325/?p=7fd98b01480f49e2925f36393c999a72&pi=3
http://blog.agiledad.com/2009/07/cost-of-bug.html
