I had to think seriously about this, because this is data that could, potentially, make an agent (me) look bad. Very bad. Very very very bad. Worthy of hatemail and scorn and bad karma and tossed tomatoes. Do I know how hard it is to write 200 pages? Well, sort of. (I've considered cranking out 200 pages just so I know.)
For the greater writer good, I am risking wrath and giving you an inside look into what actually happens when we receive your manuscripts--and I will make a line graph of the number of pages it usually takes me to reach a decision about whether a manuscript works or not.
You see the potential for unpopularity: no one wants to write 300 pages, only to be rejected after the reading of one. Alternately, no one wants to assume that we get to page 299 loving it--and then there's a twist that changes everything--so close, so close and yet so far! (Truth be told, if we get to 299 and love it except for page 300, the vast majority of us would tell you how to fix it. So don't worry too much about that. Also, unless you insult me personally in the first page, I will read more.)