Find opportunities for improvement in software development by first figuring out which problems are development problems. XP isn't intended to solve marketing, sales, or management problems. It's not that non-software bottlenecks aren't important, it's just that XP doesn't spread that thin. There may be ways to crank the knobs to 10 in other areas too, but that is outside the scope of XP. XP is a coherent body of values, principles, and practices for addressing software development problems. We need a way to look at software development as a whole.
One approach to looking at the throughput of entire systems is the Theory of Constraints. I'll illustrate the theory with an example from my own laundry room (