[FotoPlasma]

Dan: You're making the assumption that the "crop," at any given time, consists of the entire population of the Earth, which isn't necessarilly true.

The machines could keep only 2.5million humans in power plants, in which case, 250,000 is a huge portion (relatively). 250,000 is 0.1% of 250,000,000. And that's still under the assumption that the population of Zion came from the Matrix, when, in fact, not all of it did. You know that both Tank and Dozer, from the first movie, were born and raised in Zion, and have never, in their lives, been in the Matrix.