Author Laurell Hamilton writes in her blog:
There are two main methods that writers choose for deciding how to measure their productivity on a book. One, is page count, how many pages you can do per day. Two, is at this time of day you sit down and you can’t get up again for two hours, or four hours, or whatever. Or a variant of method two, is whatever time you sit down at your desk you work for two hours, and until two hours are up, you cannot leave your desk. Yesterday was a day that reminded me why I’ve always done page count and never hours at the desk…
Laurell is a "Page Count" person because her day is too hectic and unpredictable to schedule a block of uninterrupted writing time. Me, I don’t use either method. I just ask myself if I feel I’ve done good work today… or at least given it my best effort. (Or, in the case of a TV script, at the rate I am going, will the teleplay be ready in time for Prep?)
I don’t think that five pages of shit or eight hours spent staring at the screen until your eyes are bloodshot really measures anything. For me, it’s quality, not quantity, whether you’re measuring pages or hours. What about you?