I've been using a number of average words per day from a paper in Science that appeared a few weeks ago; well, here's the paper. It's (provocatively) titled, "Are women more talkative than men?" The answer is no: both men and women in a sample of 396 college students said the same number of words, an average of around 16,000.

Phone lines are open if you want to complain that 396 college students are not representative of the population as a whole.