A few years ago, before Windows XP, another new programming methodology called Extreme Programming (or XP) was popular. It involved having two programmers work at a single terminal, both working on the same code at the same time. Its advocates claimed that this had been proven in many companies to increase overall productivity.
I'd puzzled for some time over how this could possibly increase productivity, when, walking around the office one day recently, it hit me. It doesn't have to increase productivity per hour worked. It just has to increase the number of hours worked. When there are two people at the terminal, neither one can say, "Give me a second here while I check my email... read Dilbert... check SlashDot... update my LiveJournal."
If XP increases average programmer productivity, what I think that really means is that the average programmer works less than half the time they're at work.