From your experience, of those industries that develop custom software for internal use such as financial services companies, which ones produce higher quality software measured in defect rates and, more qualitatively, ease of maintenance over the long term?

What contributes the most to this achievement of higher quality? Is it due to better software development practices such as greater emphasis on testing or specification? Developers who better understand the tools or who are strong problem solvers? Better communication between team members?

On the flip-side, which industries do you think produce the lowest quality software? Why?