and from Robert L Glass, Facts and Fallacies of Software Engineering (2003, but I think a self-reference from Building Quality Software, 1992): "The data on th

and from Robert L Glass, Facts and Fallacies of Software Engineering (2003, but I think a self-reference from Building Quality Software, 1992): "The data on the percentage of time spent in error removal has varied over the years, but the usual figures are 20-20-20-40. That is, 20 percent for requirements, 20 percent for design, 20 percent for coding (intuition suggests to most programmers that here is where the time is spent, but intuition is very wrong), and 40 percent for error removal."