Tom DeMarco :

My early metrics book, Controlling Software Projects: Management, Measurement, and Estimation (Prentice Hall/Yourdon Press, 1982) , played a role in the way many budding software engineers quantified work and planned their projects. […] The book’s most quoted line is its first sentence: “You can’t control what you can’t measure.” This line contains a real truth, but I’ve become increasingly uncomfortable with my use of it.

Implicit in the quote (and indeed in the book’s title) is that control is an important aspect, maybe the most important, of any software project. But it isn’t. Many projects have proceeded without much control but managed to produce wonderful products such as Google Earth or Wikipedia.

To understand control’s real role, you need to distinguish between two drastically different kinds of projects:

Project A will eventually cost about a million dollars and produce value of around $1.1 million.

Project B will eventually cost about a million dollars and produce value of more than $50 million.

What’s immediately apparent is that control is really important for Project A but almost not at all important for Project B. This leads us to the odd conclusion that strict control is something that matters a lot on relatively useless projects and much less on useful projects. It suggests that the more you focus on control, the more likely you’re working on a project that’s striving to deliver something of relatively minor value.